For the last three seasons of television, This Is Us has been one of the breakaway hits, pulling in enormous amounts of viewers, passionate online fans, and awards and nominations by the dozen. The NBC family drama series follows the lives of the extended Pearson family, a story that spans multiple generations and time periods and seamlessly navigates back and forth between them. All together, the action has thus far spanned nearly a century, with flashbacks as far back as the 1940s and flash forwards to at least the 2030s or 2040s.

Unlike most series on air, therefore, This Is Us has had perhaps some of the most pressure in the casting department. As characters age and grow from generation to generation, different actors are required to play the same characters in childhood, adolescence, and adulthood. Certain characters, however, haven't had to experience multi casting as they've only occurred in one time period. And ironically, some of those casting choices have been the weakest of them all.

For the most part, the series has been pretty lucky in the casting department, and the number of award nominations and wins alone reaffirms that. But sometimes, even the most successful of series can really miss the mark.

Here are 5 Casting Decisions That Hurt This Is Us (And 15 That Saved It).

Saved: Susan Kelechi Watson - Beth

Beth Pearson looking serious in This Is Us

The character of Beth Pearson is one that could have gone terribly wrong, had it not been for the right actress being chosen for the job. As the voice of reason in the often hyper emotional Pearson clan, Beth often stands in direct opposition with fan favorites such as Randall or Kate.

However, her down to earth demeanor and frank expression of feelings and opinions make her a truly needed character, and Susan Kelechi Watson's acting always elevates her to a whole other level. Watson works perfectly off every screen partner she's given, and in recent episodes, she's really begun to pull back some of the layers on Beth's character to show viewers what's inside.

Saved: Niles Fitch - Randall

Niles Fitch as Teenage Randall Pearson in This Is Us

From the very beginning, Randall has been the beating heart of the series. While much of that has been credited to the actor responsible for adult Randall's work, Sterling K. Brown, viewers would be remiss if they didn't also give some of that much-deserved credit to the young man behind teenage Randall, Niles Fitch.

As teenage Randall, Fitch shows viewers sides of Randall that we don't often get to see when he's an adult. Teenage Randall struggles more openly with his anxiety, with the subject of race and fitting in, and with how to become the man he wants to be in his father's image. Teenage Randall is a character navigating the minefield of his transitional years, undergoing countless hardships along the way, and Fitch performs each and every taxing scene with the refined talent and grace of a seasoned pro.

Saved: Chrissy Metz - Kate

This Is Us Chrissy Metz

Kate has had one of the most emotionally raw journeys out of any members of the extended Pearson clan. Her lifelong struggle with her weight has led to some particularly heartbreaking moments, such as adult Kate losing her first baby and the frightening journey toward pursuing pregnancy again on her own terms, despite the risks. She's also had to deal with profound amounts of guilt after Jack's passing, since she blames herself for it all for multiple reasons.

She's also dealt with career ups and downs, a fractured relationship with her mother, and the needs of both her emotionally complicated brothers. All the while, Kate is portrayed with breathtaking sincerity and vulnerability by Chrissy Metz. Whether singing her heart out or pouring it out in a heart to heart with Toby or her brothers, Metz is truly one of the series' most talented assets.

Hurt: Jon Huertas - Miguel

Whoever the series cast in the role of Miguel Rivas was bound to have an unenviable role no matter what. As the often overly honest best friend of Pearson patriarch Jack, Miguel is usually a source of eye rolls and nothing more. In the present timeline, as Rebecca's second husband and the uncomfortable stepfather to the Big Three, Miguel now becomes a source of confusion and, if social media is anything to go by, considerable scorn.

Jon Huertas spent eight years prior to his turn on This Is Us on the ABC comedy/drama/action series Castle. He's proven that he's clearly qualified for handling certain heavy material. However, for some reason, Miguel's narrative is outside of his wheelhouse, making the character come across as much more awkward and out of place than he was perhaps intended to be.

Saved: Chris Sullivan - Toby

This Is Us Chris Sullivan

Most of the time, Toby Damon feels like a character who exists only to provide comic relief -- even if not everyone finds his jokes funny, or appropriate, or suited to the moment at hand. His brand of offbeat humor is something that actor Chris Sullivan excels at, nailing each and every line delivery no matter how awkward the scene may be. However, time has shown that it's not just comedy that Toby's character was meant for.

In recent arcs, such as during Toby's spiral into depression after going off his medication and during Toby and Kate's quest to conceive a child, Sullivan has shown all that he is really capable of, when provided serious enough material. It's nice to have Toby's sense of humor to depend on all the time, but it's also refreshing to see that Sullivan is willing to step up to the drama plate whenever needed, too.

Saved: Jermel Nakia - William

Jermel Nakia as Young William Hill in This Is Us

William Hill has proven himself to be one of the most integral characters in the entire series so far, even if his relation to the Pearson family has undergone multiple difficult iterations with time. As Randall's biological father, William provides Randall with many of the answers and emotional connections he has been looking for his entire life, once they meet in the present timeline.

However, in the past, as masterfully played by Jermel Nakia, William is a man at war with himself and his way of life. Viewers witness Nakia's William go from starry-eyed and in love poet, to lost and broken addict, to aimless new father, to recovering artist making an honest life for himself and desperately seeking to right the wrongs he'd once made. In Nakia's talented hands, not one of these versions of William feels any less believable than the other.

Saved: Lyric Ross - Deja

Deja Pearson giving side eye in This Is Us

When Deja first entered the series, her character was met with much apprehension, seeing as she fundamentally shook up the family dynamic that viewers had come to know and love in Randall and Beth's home. Her transition from foster child to adoption was a tremendously difficult one, given the heartbreaking backstory that was revealed over time regarding her relationship with her mother. The fights Deja had with her new family were likewise incredibly difficult to endure, given all the emotion built up between them.

However, all the while, Lyric Ross proved herself to be quite the capable young actress. Her emotional range has been nothing short of astounding, as Deja navigates heartbreak and loss and relief and joy, sometimes in the blink of an eye.

Hurt: Michael Angarano - Nicky

Michael Angarano as Nicky Pearson in This Is Us

Viewers have known from early on in the second season of This Is Us that Jack's younger brother, Nicky, never made it back home from Vietnam. Of course, recent episodes have challenged that belief, but that's not the point here. The third season introduced viewers to an adolescent version of Nicky Pearson, played by Michael Angarano. Nicky was softer than his brother in many ways -- more of a hippie and physically weaker than Jack, which made Vietnam a terrible fit for him.

However, while the show has told us all of these things, Angarano's performance has never really shown us them. Living in Jack's shadow in Pennsylvania, Angarano's Nicky is so subdued and quiet that there's almost nothing to him. As a burn out in Vietnam, Angarano's Nicky is manic and impossible to connect with.

Saved: Faithe Herman - Annie

Faithe Herman as Annie Pearson in This Is Us

Annie Pearson is a character who is often in the background of important moments, but somehow, she always finds a way to steal the spotlight and win over the hearts of fans everywhere. Whether simply making a cute joke while sporting one of her adorable flower hairclips, or in heartwarming moments such as a rare and precious flashback scene between her and William, Annie has proven herself to be the heart and soul of the next generation of Pearsons.

None of it would have been possible without the casting of Faithe Herman, the smallest and perhaps youngest member of the entire extended cast. Already a pint size powerhouse, Herman holds her own against her much older and seasoned costars, making Annie a vital member of the cast and sorely missed when she's not around.

Saved: Mackenzie Hancsicsak - Kate

Mackenzie Hancsicsak as Young Kate Pearson in This Is Us

Another of the series' youngest cast members has routinely turned in some of its strongest performances. As Kate when she was a little girl, Mackenzie Hancsicsak gets to play some surprisingly weighty scenes, especially opposite her parents, Mandy Moore's Rebecca and Milo Ventimiglia's Jack. Already struggling with her weight and self-image from this young age, Hancsicsak's Kate has a wide eyed innocence and warmth to her that will be chipped away at over the years as Kate experiences hardship after hardship.

However, the youngest iteration of Kate has a profound love for and connection with her father, serving as a source of inspiration and vulnerability for the often closed off Pearson patriarch. Some of Jack's most significant moments have occurred opposite this tiny scene stealer, and with anyone else but Hancsicsak in the role, they would never have felt as powerful as they do now.

Saved: Mandy Moore - Rebecca

Rebecca upset

We wouldn't blame you if you were initially wary of Mandy Moore's casting as a lead in the series. Best known previously for turns in cheesy romantic comedies like Chasing LibertyA Walk to Remember, and License to Wed, Moore was always better suited to voice over work and her prominent singing career. As it turns out, however, it was just a matter of time before she found the right material - and the role of Rebecca Pearson happens to be just that.

Unlike most of the other characters on the series, Moore has played Rebecca from adolescence to later years. Moore has been a consistently reliable performer, strong and full of conviction and genuine emotion -- such as the devastating, purely true to life reaction Moore gave when filming Jack's untimely passing upon walking onto set and finding Ventimiglia's body laying there for her to act off of.

Hurt: Melanie Liburd - Zoe

Melanie Liburd as Zoe in This Is Us

Joining a show partway into its run as a series regular is never an easy ask for any actor, no matter how talented or well cast they may be. However, the matter is only made worse when an actor is clearly wrong for the role -- and the role is clearly wrong for the show, at that. Beth's cousin, Zoe, was unceremoniously introduced at the end of the series' second season, with the clear intention of incorporating her as a love interest for Kevin.

Rather than develop the characters' relationship naturally, though, viewers learned when the third season started that the two had begun secretly seeing each other, banking on a chemistry that had never been there. Melanie Liburd has never once felt believable in her scenes shared with her on screen romantic partner, Justin Hartley -- and it's perhaps due to that same presumptive behavior on the series' part.

Saved: Lonnie Chavis - Randall

Lonnie Chavis as Little Randall Pearson in This Is Us

We've already talked about the strengths that we see from teenage Randall's portrayer, Niles Fitch. However, we'd be remiss if we didn't show credit where credit is due when it comes to the talent behind little Randall Pearson, the exceptionally talented Lonnie Chavis. Even though teenage Randall deals with more questions of identity and feelings of anxiety, Chavis's Randall lays the groundwork for some of these key parts of Randall's character.

He has a heartbreaking sort of innocence, especially in his pursuit to find his biological parents, and his knowledge of his own difference from the rest of his family. He deals with being an outsider, which leads to feelings of anxiety that have allowed for some of the series' most touching father-son moments. All the while, Chavis entirely steals the show, never once coming off as anything less than the best of the best.

Saved: Eris Baker - Tess

Tess Pearson looking serious in This Is Us

Perhaps one of the biggest surprise talents in the entire series has been a recent revelation: Eris Baker, who stars as Randall and Beth's elder daughter Tess. In recent episodes, however, Baker has gone from being a background player to a young adult with a promising storyline all her own. Tess is now struggling with puberty and coming of age, but it was one particular revelation that finally allowed Baker to shine.

In a quiet moment with her aunt Kate, and in a later tearful scene with both of her parents, Baker's Tess came out, revealing that she felt so uncomfortable recently as all of her friends start to like boys, because she doesn't like boys. Instead, she likes girls. In these few but powerful scenes, Baker has suddenly transformed herself into a true talent to watch, and Tess into one of the series' most complex characters of all.

Saved: Gerald McRaney - Dr. Katowski

Gerald McRaney is perhaps the most prominent and seasoned talent in the entire cast. With a lengthy filmography including defining turns in Simon & Simon, Major Dad, Jericho, and Deadwood, McRaney has been a reliable source of gravitas and emotion across all media. However, it wasn't until his appearance as Dr. Nathan Katowski in This Is Us that the world began to really appreciate what McRaney was capable of, resulting in an Emmy award for Outstanding Guest Actor in a Drama Series.

As the ever comforting Dr. K, McRaney was nothing short of a revelation. Whether comforting new parents Jack and Rebecca on the loss of their third child, revealing the heartbreaking truth behind Dr. K's own home life and backstory, or offering words of condolence to Rebecca following Jack's sudden passing, McRaney's Dr. K. is one of the series' most reliable performers, one whose presence is ever welcome.

Hurt: Janet Montgomery - Olivia

Janet Montgomery as Olivia in This Is Us

Kevin's love life has long been one of the series' weakest spots. However, perhaps the worst choice of them all in terms of his love interests was the casting of Janet Montgomery as Olivia, a condescending, overly snarky, judgmental stage actress who worked opposite Kevin in his first foray into the theatre scene. The two were meant to have a love/hate relationship that viewers would preumably root for, since the trope is often beloved and fairly common.

However, by casting Montgomery in the part, the series all but guaranteed that no sympathy would ever be won toward the character. Often feeling as though she was over acting in any line she delivered, beyond the cloying theatrics associated with theatre types, Montgomery's Olivia was just about as unlikable as they come.

Saved: Ron Cephas Jones - William

Few characters have had more lasting an impact on the series of This Is Us than William Hill. Though sadly no longer with us, the series is smart enough to know that it could never let the supremely talented Ron Cephas Jones go, finding as many excuses as they can to incorporate flashback sequences with Randall's biological father whenever possible. William was a character who lived a long, difficult life, dealing with countless losses but remaining hopeful even in the face of hardship.

Through his late in life connection with his biological son, Randall, William infused the series with some of its most meaningful discussions of life, love, and humanity -- and also provided the series with perhaps its best episode to date, "Memphis". Jones's stellar work is also one that has been rightly recognized on multiple occasions by awards shows, including an Emmy for his work in the second season.

Saved: Milo Ventimiglia - Jack

This Is Us Jack Pearson

Milo Ventimiglia first appeared on the TV scene as bad boy Jess Mariano on Gilmore Girls, before moving on to become unlikely superhero Peter Petrelli on the onetime cult hit series Heroes. However, it wasn't until This Is Us premiered that Ventimiglia truly found the role of a lifetime in Jack Pearson. Impossibly earnest and damaged all at the same time, Jack is one of the most human characters in the entire series, fully flawed and realistic.

Ventimiglia plays Jack across the spectrum of adolescence into adulthood, and the difference of demeanor in young Jack versus adult Jack is striking. Ventimiglia imbues each of Jack's different personas and life stages with the necessary levity or gravitas, stubbornness or acceptance, hate or love. Jack has been through quite a lot in the span of his sadly too short life, and Ventimiglia makes each and every event feel just as important as the last.

Saved: Sterling K. Brown - Randall

Black Panther Will Be 'Something Special', Says Sterling K. Brown

What can we say about Sterling K. Brown that hasn't already been said thousands of times before? From the very beginning of the series, Brown has been something to behold -- a tour de force in acting in all its forms. Randall is far and away the series' most well rounded character. The highs and lows of his life have been endless, and Brown handles them all with eager grace and endless talent.

Whether on the brink of a nervous breakdown and breaking hearts everywhere, proving that he's one of TV's best husbands and fathers in a very long time, or cracking some truly nerdy jokes, Randall is always filling the series with a necessary dose of heart and warmth. None of that would have been possible without Brown's master class of acting leading the way. The countless awards and nominations the role has earned him certainly agree.

Hurt: Justin Hartley - Kevin

Kevin has routinely been the weakest link in the Pearson family tree since the series began, regardless of what age period viewers are seeing him as. However, it's in his adult form, as played by Justin Hartley, that the contrast between Hartley and his other costars stands in the starkest contrast. At times, Hartley feels capably cast in this role -- particularly in moments when Kevin is allowed to show his comedic side.

However, in more serious arcs, such as Kevin's spiral into alcoholism or his quest for the truth about his father's time in Vietnam, Hartley doesn't quite live up to the needs of the role. It's a shame, really, since Hartley has previously excelled in dramatic moments required of him in the role of Oliver Queen on Smallville. However, the heavy lifting required of him by Kevin's storyline has never been something Hartley can manage.

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Which casting choices do you think hurt or saved This Is Us the most? Let us know in the comments!