Every time a television series introduces a new character to the fold, the writers are taking a gamble. Typically, it means that the show was popular enough to make it out of its first season, and a new character can muck with the precarious balance that drew fans in the first place. There's simply no way for writers to get it right every time, meaning that in just about every show, there's a newer character that had a negative impact on the series.

The CW, the TV network formed from the merging of The WB and UPN, has been around for over a decade now, and has turned out dozens of successful (and not so successful) shows, mostly aimed at the teen demographic. Their most famous cultural exports involve superheroes, monsters, and extremely attractive actors, shows like Supernatural, Gossip Girl, The Vampire Diaries, and the Arrowverse.

Frequently, these shows' success is dependent on their casting of likable actors in well-written, compelling roles. Even the best TV show needs to inject new characters every now and then, and so CW shows tend to be made or broken by the characters they add in later seasons.

This list comprises the best and worst of those new character additions; roles that negatively impacted entire seasons and roles that seemed like a course-correction to the show we know and love today. Some are minor characters, some were elevated to the main cast, but all had an outsized impact one way or another.

These are 11 New Character Additions That Hurt CW Shows (And 9 That Saved Them).

Hurt: Damien Darhk – Arrow

Arrow Neal McDonough Damien Darhk

If you're going to use a character whose is Damien Darhk, then you'd better succeed in making him seem scary. Darhk got a lot of build-up in season four of Arrow, being an ageless magician akin to Ra's al Ghul, and he did terrible things in the season itself, but he was just never terribly interesting.

Played by veteran bad guy (and occasional Howling Commando) Neal McDonough, Darhk seemed more like a greedy tycoon than a sinister sorcerer.

The real problem with the character was that he had too many shoes to fill-- magician, assassin, immortal, mayor, crime kingpin, etc.

Add the fact that he was responsible for the end of Laurel Lance, and he was a net negative for Arrow-- though he was a bit more fun in Legends of Tomorrow).

Saved: Klaus – The Vampire Diaries

This one should come as no surprise. Niklaus Mikaelson (better known as Klaus) was a new character so important to The Vampire Diaries that he ended up starring in the spinoff show, The Originals. 

Played by Joseph Morgan, the original vampire was one of the best antagonists and one of the best protagonists the franchise ever produced.

The original hybrid had a lot going on, most notably a curse that required a sacrifice, which drove much of his actions. Klaus was one of the most interesting characters to appear on either The Vampire Diaries or The Originals, and it didn't hurt that he was also one of the most powerful supernatural beings around.

It's no wonder he got his own show to star in after The Vampire Diaries wrapped.

Hurt: Bela – Supernatural

Supernatural Dean and Bela

It wasn't a bad idea to introduce integral female characters to the bro-centric series Supernatural, but the way they did it left a lot to be desired. Bela Talbot was not the first in a line of women on Supernatural who wound up with very unfortunate fates, mainly due to negative fan response.

Much like Ellen and Jo Harvelle before her, Bela instantly became a recurring character, but her conniving ways didn't sit well with fans.

More a tricky rival than an ally, Bela was always in it for herself, partially due to the hellhounds on her trail.

The character is representative of Supernatural's inability to write affecting female characters, but at least she got a tragic (if slightly rushed) end to her story.

Saved: Lexa – The 100

The riskiest kind of character a TV adaptation of a book series can add is an original creation. When done right, original can pay big dividends in terms of narrative, sometimes becoming just the push the show needs.

Lexa was one of the success stories-- until the end of her arc, that is.

The 100 has always been a shockingly bold and complex show, especially when it comes to morality, pushing its characters to make devastating, horrific choices. Lexa, played by Alycia Debnam-Carey, might just be the poster child for that approach.

Unfortunately, Lexa and her relationship with Clarke Griffin were so popular (especially with the LGBT fanbase) that when she was bumped off it might very well have alienated many viewers.

Hurt: The Black Hood – Riverdale

Riverdale's second season was uneven, to put it mildly. While it did have some memorable highs (more on that later), the season took several turns that left fans scratching their heads. There was, of course, the introduction of "jingle jangle," an illicit stimulant that always sounded silly, but there was also the Black Hood.

The Black Hood, a masked vigilante gunman who offed those he believed had "sinned," appeared to be the show's attempt to take on the superhero genre.

While it may not have been entirely his fault that the season spun out of control, all kinds of weird stuff (a for-profit prison subplot, Archie trying to become a crime fighter, etc) happened afterward. The Black Hood is emblematic of the strange turns the season took.

Saved: Castiel – Supernatural

Those who have never seen Supernatural but are familiar with the fandom might think that Castiel was part of the main cast of the show from the beginning-- they'd be wrong.

The wayward angel actually didn't make his first appearance until the fourth season.

He was originally intended to have a short arc of just a few episodes.

Obviously, Castiel was a huge hit with fans, and ended up joining the show for much longer than originally planned. Cas is still part of the main cast going into season 14, and his bond with the Winchester brothers is as strong as ever.

His arrival changed the show forever, in the best possible way, making him a slam-dunk candidate for this list.

Hurt: Mon-El – Supergirl

The prince of Daxam doesn't have a bad character arc, as a womanizer who learns to put duty first and open up emotionally, but the fact is too much time was wasted on Mon-El before he got to that point. Mon-El took screen time away from the established supporting characters and, worst of all, Supergirl herself.

Sometimes first impressions matter just as much as growth: Mon-El started the show as a misogynistic, classist egotist, and it's hard to recover from a first impression like that. His unnecessary love triangle with Imra and Kara was more than a little tiresome.

Many fans were relieved when it was announced that Chris Wood would not be reprising the role in the upcoming season four.

Saved: Darci – Jane the Virgin

She may be better known today for her starring role on Netflix's One Day at a Time, but Justina Machado has more than one great TV role in her filmography. Her performance as Darci Factor on Jane the Virgin was an immediate hit with fans.

A no-nonsense matchmaker, Darci went through a wringer with Rogelio as first she tried to find a match for him, then entered into a non-romantic co-parenting agreement with him, then dated him, before he broke it off with her.

Justina Machado has been a welcome presence on just about every TV show she's been on, especially in recent years, so is it really a surprise that she imbued this character arc with all kinds of humor and emotion?

Hurt: Davis Bloome – Smallville

Doomsday as Davis Bloome in Smallville

Somewhat infamous in the Smallville fandom, Davis Bloome may not look like much, but he's hiding a big secret. Namely, that he is the human-shaped "camouflage" for one of the most powerful DC supervillains, Doomsday.

There's just no way around it: when it came to depicting the beast that took out Superman himself, Davis was nothing but a letdown.

An early performance from Sam Witwer, who went on to much better things, Davis was generally awkward to watch on screen. He had weird interpersonal relationships-- which were not helped by his abducting habits-- and wasn't particularly compelling. T

he season eight addition might have been engaging in his own right-- and the same goes for Doomsday-- but the combination of the two never worked out.

Saved: Alternate reality Harrison Wells – The Flash

The Flash Season 4 Harrison Wells

Tom Cavanagh has been one of the most entertaining parts of The Flash since season one, even when he was playing Eobard Thawne masquerading as Harrison Wells. When that character was defeated at the end of the season, fans were paralyzed with the fear that Cavanagh might not return.

Thankfully, the writers have since found endless ways to get Cavanagh back into the fold. Earth-Two's Harrison Wells was introduced in the second season, and there have been over a dozen other Wellses from alternate realities since then.

Whether it's as a gruff scientist/mentor or any one of an array of zanily accented comic relief characters, Harrison Wells is always welcome in The Flash.

Hurt: Echo – The 100

One of the common themes on this list is characters who were deceitful or manipulative during their time on their respective shows. Maybe it's just a bad habit CW shows have, but Echo definitely fits that mold.

First introduced in season two and later bumped up to main cast status, Echo is played by Tasya Teles on The 100. 

Echo was a Grounder loyal to the Azgeda warriors, though she was later banished. Fans were mixed on her character when she was just known for complicating the plot, but their reaction became much more negative when she struck up a relationship with Bellamy.

Despite the two characters bonding, fans just didn't think the pairing made sense for either character.

Saved: Julian Baker – One Tree Hill

One Tree Hill, the series that started in 2003 back when The CW was still called The WB, was known for making huge changes to its character dynamics between seasons. Beyond the jumps forward in time and the shift away from basketball as its main focus, there were also introductions of characters who became much more important than they initially appeared.

One of those was Julian Baker, a handsome film producer who arrived in town to make the adaptation of Lucas Scott's book. He quickly became interested in Lucas' ex, Brooke, in a romance that seemed destined to fizzle out when he returned to LA.

Fans enjoyed the couple, though-- especially how happy it seemed to make Brooke-- and so Julian stayed for the rest of the series.

Hurt: Catalina – Jane the Virgin

Here, again is any entry that follows the trend of characters that hurt the shows their shows being introduced in manipulative and deceitful ways. These plotlines tend to feel like a distraction from the primary narrative of a show, and Catalina Mora was definitely a distraction.

Introduced in season three, Catalina is Jane's cousin-- one that her grandmother doesn't want her to meet.

She shows up out of nowhere because she's spontaneous and impulsive, and only later does it become apparent that she hasn't been honest about her life.

When she first appeared and began a fling with Rafael that made Jane jealous, Catalina seemed like a good way to bring new conflict, but when we discovered she had to leave because of a secret marriage, it just felt like an annoyance.

Saved: Freya – The Originals

Introduced in the second season of The Originals, Freya Mikaelson instantly seemed like a promising addition to the show. Klaus' older half-sister, Freya was a powerful witch thanks to some complicated ancient magic from her aunt Dahlia. Nearly immortal, she was an immediate threat to just about everyone on the show.

Shaking up the balance of power is an important thing to do in a series like The Originals, but even beyond that initial role, fans connected to Riley Voelkel's performance as Freya even after the witch lost her initial immense power.

Much like Klaus, Freya valued family and saw the world from a uniquely black and white perspective, so it's no wonder fans liked her. Her sweet romance with her future wife, Keelin, only added to her charm.

Hurt: Mallus – Legends of Tomorrow

Mallus spreading his wings and roaring in Legends of Tomorrow

Though Damien Darhk was more fun on Legends of Tomorrow,one of his pals isn't. Mallus is an extremely powerful time demon, not unlike a primordial devil, but he wound up being a pretty trite antagonist for the Legends. 

The villain felt like a crossover between a Final Fantasy boss and a demon from Supernatural, and the combination did not work.

Of course, Mallus' main problem is that he didn't actually appear on screen for the majority of the season in which he served as a primary antagonist. Most of his episodes found him possessing someone else (usually Nora Darhk) and speaking through them.

Somehow, we got too little and too much of Mallus at the same time.

Saved: Cyrus Rose – Gossip Girl

In the novels, Cyrus Rose, Eleanor Waldorf's second husband and step-father to Blair, was described as "sweaty" and initially came off as pretty unlikable. Well, the book version wasn't played by Wallace Shawn.

Shawn first appeared in the second season of Gossip Girl, and fans immediately loved him.

Cyrus became a good step-father to Blair, even walking her down the aisle alongside her biological father at her wedding. Sometimes, all a character needs to do to be a good addition is just be nice, and Cyrus was just that.

The quirky Cyrus was funny and extremely dorky, and fans of the series were glad they got as much screen time from Shawn as they did.

Hurt: Nadia Petrova – The Vampire Diaries

This one was just a disappointment. Nadia Petrova was introduced to The Vampire Diaries in season five. She had a strong build-up, thanks to being the daughter of Katherine Pierce, one of the great villains of the series. Unfortunately, Nadia's writing wasn't nearly so competent, as she was constantly sidelined, dependent, and overshadowed by her mother, making her a secondary concern, at best.

Played by Olga Fonda, Nadia never managed to be compelling on screen.

Her overarching goals of helping her mother were boring and her actual performance was awkward and weak. This was a character that could have easily been written out and replaced with just about any other subplot.

Saved: Hiram Lodge – Riverdale

Veronica's dastardly father Hiram Lodge's arrival was always planned, as it had been teased since the very beginning of Riverdale. 

While Archie and the gang were investigating the mystery of season one, Hiram's name kept coming up in the darker corners of town. A manipulative CEO, arrested in the past for embezzlement and fraud, Hiram was always going to be one of the major bad guys of the show.

Played by Mark Consuelos, Hiram lived up to the hype when he arrived in season two. It would have been easy to make Hiram appear a mustache-twirling supervillain, but Consuelos lent Hiram a real sense of charisma and likability, which made him much more dangerous and fun to watch.

Hurt: Angus McDonough – iZombie

Want to know a really great way to make your main villain seem weaker and less interesting? Introduce his father and give him a lot of manipulative father-son subplots. That's the route iZombie chose, as Angus McDonough, the father of Blaine DeBeers, made his first appearance in season two.

Showing up pretty much out of nowhere, Angus diluted Blaine's villainous motivations from greed and psychopathic apathy toward removing people's brains to simple daddy issues.

Fan response has been mixed to Angus stepping in and creating all kinds of conflict, but the show's writers seem to like him, as they've recently upgraded the actor Robert Knepper to main cast status.

Hurt: Ivy Dickens – Gossip Girl

In season five, Gossip Girl had a problem: it lost Taylor Momsen, who played Jenny Humphrey, and needed a new character to step in and create some drama. Enter Kaylee DeFer Ivy Dickens, an actress masquerading as Charlotte Rhodes in a scam to leech some trust fund money.

Putting the inherent implausibility of that initial storyline aside (no one thought to find out what the real Charlotte looked like?), the decision to make Kaylee DeFer into a series regular was a bad one, as fans and critics alike were less than impressed with her acting.

Couple that with a universally reviled storyline, and this character definitely didn't help the show.

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Who's your favorite new CW character? Let us know in the comments!