Sitcoms face an interesting dilemma throughout their runs. The setup will only go so far before the show has to start to make changes if they want to survive long enough to become an iconic series.

Friends started out as five friends going through their daily lives, but they needed to add in new characters and situations to make it through 10 seasons. Cheers was able to get through 11 seasons of life in a Boston bar, but that would not have been possible without the addition of new characters and storylines.

While a show like Seinfeld was able to make it nine seasons without changing hardly anything, this is the exception to the rule.

With this in mind, adding new characters to classic sitcoms does not always work. There are some characters that come in and fans immediately fall in love with them. These characters add to the stories and give the audience a reason to care about both the fate of the characters and the running storyline itself.

However, there are other characters that come in and add nothing to the story. Even worse, there are characters that come in and detract from the story and drag the entire show down every time they step in front of the cameras.

While some characters extend the life of a sitcom for many years, others mark the end of the series almost instantly.

With that said, here are the 13 New Character Additions That Hurt Iconic Sitcoms (And 12 That Saved Them).

HURT: NELLIE - THE OFFICE

Toby kisses Nellie's head on The Office

After Steve Carell left The Office, the show started looking for Michael Scott's replacement.

There were good and bad options that showed up in season 8, but the worst addition to that role was easily Nellie Bertram, portrayed by Catherine Tate.

When Nellie came in, she named herself the new office manager.

Yes, Tate is a great actress but Nellie just never worked as a character -- she was rude and annoying to a fault.

There is also the fact that she started to come into her own by the end, especially when she admitted that she had no skills or education and no real ideas of her own -- so at least there was that.

However, compared to all the other options, Nellie was a huge step-down.

SAVED: FRANK - IT'S ALWAYS SUNNY

Frank in a hoodie and green shirt in It's Always Sunny in Philadelphia

It is almost hard to believe that Frank was not on It's Always Sunny in Philadelphia from the start.

Played by Danny DeVito, Frank is the father of Dennis and Dee and lives with Charlie. He partially owns and helps run Paddy's Pub and fits in well with the gang since he lost most of his morality and has no moral compass whatsoever.

The first season of It's Always Sunny had low ratings and needed something to turn it around quick. None of the cast included big names at the time and FX suggested bringing in a big name to help boost ratings.

It was FX that brought up the idea of signing Danny DeVito. While the other actors were reluctant at first, they finally gave in and the rest is history.

HURT: RANDY - THAT '70S SHOW

Ruined Performances

It seemed like things were done when both Ashton Kutcher and Topher Grace left That '70s Show after the seventh season.

However, instead of ending the show after the seventh season finale or trying to go out on a high note, the show's producers decided to just try to replace the departing stars and things did not go well.

The biggest disappointment was bringing in Josh Meyers to play a character named Randy Pearson.

Crazily, Meyers was supposed to replace Topher Grace and claim that he was Eric -- returned from Africa as a changed man.

Instead, he ended up as a new character that Donna fell for.

Overall, he was a bland character in an eighth and final season that most fans would rather forget.

SAVED: CHARLIE - SPIN CITY

Spin City was in trouble in 2000 when Michael J. Fox had to leave the show for medical reasons. Fox, an immensely popular actor at the time, left after the fourth season due to his battles with Parkinson's disease.

Replacing him in the cast was Charlie Sheen, who joined as the character Charlie Crawford.

Sheen joined Heather Locklear, who came onboard the show in the fourth season to help ease the load from Fox originally.

They helped Spin City carry on for two more seasons after the departure of Fox.

Losing Fox was tough, but Sheen and Locklear had enough star power to push the show on to the eventual conclusion.

Sheen parlayed his new television success into a monster run on Two and a Half Men, which debuted the year after Spin City left the air.

HURT: TORI - SAVED BY THE BELL

Leanna Creel as Tori on Saved By The Bell

The last season of Saved by the Bell had some interesting casting choices. The reason was simple -- Tiffani-Amber Thiessen and Elizabeth Berkley had their contracts up for renewal and they wouldn't sign on for the extra episodes needed in that fourth season.

Kelly and Jessie were there for some episodes and the series decided to add characters to replace them.

Tori was brought in as the new female lead to replace the two, as the popular girls disappeared from the series. Tori was a tomboy who rode a motorcycle and wore a leather jacket.

Having someone come in for the final season as the new girlfriend for Zack Morris was not something that fans wanted to see and the sudden change really hurt the show, which ended up finished at the conclusion of that season.

SAVED: JIM - 8 SIMPLE RULES

13 New Character Additions That Hurt Iconic Sitcoms (And 12 That Saved Them)

The sitcom 8 Simple Rules suffered the worst possible setback in 2003 when lead actor John Ritter passed away suddenly.

The show was about a couple (John Ritter and Katey Segal) and their three kids, including their teenage daughter (Kaley Cuoko) that the title references.

However, Ritter passed away in the second season of the show and the producers brought in some fantastic names to help try to save the show.

The legendary James Garner signed on as the children's grandfather, moving in to help out with the kids, while David Spade joined the cast as the kid's older cousin.

Ratings dropped in the third season, but Garner was a classy addition and really helped the show recover for a short time from the loss of its star.

HURT: THE NEW CAST - SCRUBS

Three characters from Scrubs season 9 next to each other

There have been cases where a major star leaves a show and the series tries to move on my replacing them with a new character.

However, in the case of Scrubs, the idea was taken to the extreme.

What is tragic is that the ninth season completely ruined what should have been a perfect series finale.

In the eighth season finale, JD chose to leave the hospital to be closer to his son and spent the final episode saying goodbye in scenes that had fans crying.

It was perfection. Then, for reasons unknown, Scrubs came back for a ninth season with a brand new set of doctors and the lowest ratings of its entire run.

SAVED: BEN AND CHRIS - PARKS AND REC

13 New Character Additions That Hurt Iconic Sitcoms (And 12 That Saved Them)

Parks and Recreation wasn't always a successful sitcom. While the critics always loved it and it had a loyal fanbase, the ratings were low and it was in danger of cancelation.

As a result, the series reached out and brought in two new stars for the show at the same time -- Rob Lowe and Adam Scott.

The two new characters -- Chris and Ben -- entered the show as auditors trying to help dig Pawnee, Indiana out of the financial hole it had fallen into with Chris (Lowe) as the schmoozer and Ben (Scott) as the ax-man.

While they entered at the end of the second season, the two helped reinvigorate the series and helped carry it to seven entertaining seasons.

HURT: 3J - FAMILY MATTERS

13J wears a yellow shirt in Family Matters

One thing that sitcoms like to do when they have lasted a large number of years is to bring in new kids as characters. It has been going on for a long time and it rarely ever works out.

On Family Matters, a new child actor was named to the cast in the seventh season and he became a main cast member by season eight.

By this time, Family Matters had become the Steve Urkel show -- the former recurring character from season one becoming the main focus of the series in its later years.

By the seventh and eighth season, all the kids that the show centered on had grown up and 3J became the new kid -- an orphan who wanted a real family.

The story was supposed to see him reunited with his birth mother but it was canceled before that could happen.

SAVED: MAX - NEWSRADIO

13 New Character Additions That Hurt Iconic Sitcoms (And 12 That Saved Them)

NewsRadio was another popular sitcom that found itself at a crossroads following the passing of the show's main star.

Phil Hartman, the former Saturday Night Live cast member, headlined the show as Bill McNeal, a popular radio news anchor.

After the fourth season, the show ended up getting picked up for a fifth season but Hartman's untimely passing put a damper on the celebration.

Hartman actually picked up an Emmy nomination posthumously for his performance on the show.

NewsRadio continued on for one more season with Hartman's friend Jon Lovitz replacing him and he brought some new energy to the final season -- something that would have been impossible without someone of his comedic talents.

When asked, Lovitz said that he took the job because he was doing it "for Phil."

HURT: NICKY AND ALEX - FULL HOUSE

13 New Character Additions That Hurt Iconic Sitcoms (And 12 That Saved Them)

There were a lot of things that made Full House one of the most popular sitcoms on TV for many years. Most of it had to do with the comic talents of Bob Saget, Dave Coulier, and John Stamos mixed with the coming of age of the young stars Candace Cameron and Jodie Sweetin.

However, it seemed that a lot of people thought the biggest draws were the Olsen twins.

Mary-Kate and Ashley Olsen played the toddler Michelle, alternating when the show needed the toddler to wander into a scene and say something cute.

This was great in limited doses, but over time, Full House depended on it too much.

When Michelle got older, Full House decided to add a new set of twins, as Uncle Jesse and Rebecca had kids of their own -- but it was never as cute as the first time around.

SAVED: DOUG - BROOKLYN NINE-NINE

Craig Robinson The Office

Brooklyn Nine-Nine has been one of the top-rated comedy sitcoms of recent years, but it always seemed to fight season after season to avoid cancelation.

Even when Fox finally pulled the plug on the show, NBC stepped up and saved the popular sitcom.

The cast was already great, but when they added Craig Robinson as Doug, it added even more quality to the series.

Robinson played a bad guy known as the Pontiac Bandit, a car thief who became a quick fan favorite.

On the series, Jake (Andy Samberg) had been chasing the thief for years and he ended up as not only a great nemesis but also a friend and partner in the time of need.

Robinson, who has appeared on a lot of great shows in his career, stole the scene every time he showed up on screen.

HURT: CRISS CHROS - 30 ROCK

One of the most fun things to watch throughout the seven seasons of the sitcom 30 Rock was the various romantic relationships for Liz Lemon.

She has dated characters played by everyone from Wayne Brady and Jason Sudeikis to Jon Hamm and Matt Damon. When it comes to Liz having no idea what she wants in a man, there was a lot of gold to mine.

However, when she finally got married to Criss Chros, it destroyed the part of her character by making her seemingly happy.

What really hurt 30 Rock was that they didn't show Liz and Criss when they started dating and only introduced James Marsden's character after the two already started dating.

This countered the story that was built about Liz not being able to find a good man. Add in the fact that Criss was boring, and he landed with a thud for fans of the show.

SAVED: AMY AND BERNADETTE - THE BIG BANG THEORY

The Big Bang Theory is the sitcom that people love to claim that they hate. Despite this, the show has never had to bother finding fans to watch it, as the people who love the series greatly outnumber those who lambast the sitcom.

With the upcoming 12th season set to be its final season, there is a good reason for its longevity. The cast remains iconic and this includes two characters added in season 3.

For the first two seasons of the sitcom, the entire show centered around the group of geeky male friends and their relationship with a female neighbor named Penny (Kaley Cuoco).

After two years, that had the chance to get a little too creepy and as a result, two more females were added in Amy and Bernadette in season 3.

This gave romantic interests to Sheldon and Howard. It also gave the show legs.

HURT: SEVEN - MARRIED... WITH CHILDREN

13 New Character Additions That Hurt Iconic Sitcoms (And 12 That Saved Them)

What made Married... with Children work so well was the four-member family unit of Al and Peg Bundy and their hapless kids Kelly and Bud.

Al was the former high school football star who hated his life, Peggy was the obnoxious wife, Kelly was clueless, and Bud was a complete loser. There were also the crazy neighbors, but the entire comedy came from this dysfunctional family involved in very non-PC situations.

Then, in the seventh season of Married... with Children, the sitcom made a poor decision when they added a fifth member of the Bundy family in the child Seven.

The setup was funny with his parents dropping him off and then not returning, but fans hated the character so much that the series actually just wrote him out without much of an explanation.

His best appearance was on a milk carton with the words "missing" after he left the show.

SAVED: WALDEN - TWO AND A HALF MEN

Charlie Sheen started to lose control and turned Two and a Half Men creator Chuck Lorre against him.

After a series of bizarre interviews and insults dished out against Lorre, Sheen was fired from his own television series.

Though Sheen was the highest paid TV star at the time, Two and a Half Men not only fired him but offed his character at the hands of a train, with him exploding "like a balloon full of meat."

Then, the show chose to move on without Sheen by casting former That '70s Show star Ashton Kutcher as Walden -- his replacement.

Walden is a billionaire who shows up on Alan's doorstep after Alan learns that their house has a mortgage he can't afford, a perfect coincidence.

It worked too and the show lasted four more seasons.

HURT: EMILY - FRIENDS

There are two additions to the successful sitcom Friends during its 10-season run on NBC that fans hated.

The first was Paul Rudd's Mike, the character that ended up marrying Phoebe in the final season. Of course, Paul Rudd remains a national treasure, so while he was not a good addition to the show, he's often glazed over by most fans.

Emily Waltham ended up as one of the most despised characters on Friends and a lot of it is because of her character's purpose on the series.

Emily tried to force Ross to never see Rachel again, which made her a character who tried to split up the group.

It also led to one of the most cringe-worthy moments of the series when she was set to marry Ross and he said Rachel's name by accident.

SAVED: JEFFERSON - MARRIED... WITH CHILDREN

Married... with Children made some bad moves in its lengthy history. However, one character addition that worked great was Jefferson Milhouse D'Arcy.

This is a slight shock since he was portrayed on the sitcom by Ted McGinley, whose reputation as a show ruiner has become the thing of legend.

However, with that said, his addition to Married... With Children was a huge boost for the series.

In the middle of the fourth season, Steve left Marcy and became a forest ranger. His replacement was a much better character for the show, with Jefferson being a boy-toy for Marcy, who was basically the male equivalent of Peggy Bundy.

This show ruiner shook his reputation by lasting seven seasons on the show and bringing it a great character to play off Al Bundy.

HURT: REAGAN - NEW GIRL

What made New Girl so great was the performance of Zooey Deschanel in the lead role When Deschanel became pregnant in 2016, she was replaced in the show by Megan Fox -- someone who was completely opposite from the sitcom's star.

What is most interesting is that Fox started off great on the show as Reagan and even stuck around.

Sadly, the entire storyline of her character focused on her being attractive.

She also worked for most of the show as the straight character that the others could play off of.

Thankfully, when Jess returned to the series, her weirdness was back and things on New Girl got back to normal. Fox is much better in the supporting role behind Jess, though, but not as the lead character.

SAVED: WINCHESTER - M*A*S*H

There were three major changes to the cast of M*A*S*H during its very successful 11-year run.

The popular TV sitcom, a spinoff of the Robert Altman movie from 1070, followed the exploits of the 4077th Mobile Army Surgical Hospital during the Korean War.

The three major casting changes included Hawkeye Pierce's best friend, his primary antagonist, and his commanding officer.

Sherman Potter replaced Henry Blake as the commanding officer in one of the most depressing episodes of the series when Blake perished on his way back home.

B.J. Hunnicutt replaced Trapper John McIntyre as the best friend of Hawkeye. However, the best move was when Winchester replaced Frank Burns, making the main antagonist less evil and more nuanced.

All three changes were all improvements for the sitcom.