10 Popular TV Characters Not in the Original Cast

Adding fresh faces to a show already on the air can be a tricky move. Sometimes it works wonders, but other times it falls flat. Remember the ‘Cousin Oliver’ effect from The Brady Bunch? That term describes late additions meant to liven things up, often with less-than-stellar results. Yet, not every latecomer spells doom. For every character fans wish they could forget, there’s another who steals the show and becomes absolutely iconic.

Let’s dive into ten fan-favorite TV characters who joined their shows after the pilot but ended up capturing our hearts. Fair warning, a few spoilers lie ahead!

10. Frank Reynolds: It’s Always Sunny in Philadelphia

It’s Always Sunny in Philadelphia stands as one of TV’s longest-running comedies, now boasting over 15 seasons. It’s quite the success story, especially considering its humble beginnings. Back in the early 2000s, creators Charlie Day, Glenn Howerton, and Rob McElhenney were actors trying to make it, shooting home movies together. This led to the idea for It’s Always Sunny.

They shot a pilot on a simple camcorder, and FX picked it up. However, viewership was slow initially. The network felt something—or someone—was missing. That’s when Danny DeVito stepped in.

Joining in season 2 as Dennis and Dee’s stepfather, Frank Reynolds, DeVito brought a character completely different from his usual friendly public image. Frank is rude, vulgar, and utterly cynical, fitting perfectly into the show’s dark humor. Despite the original cast’s initial doubts, adding DeVito is widely credited with saving the show from cancellation. Many fans feel Frank Reynolds was the missing piece that turned a good show into a truly great one.

9. Ben Linus: Lost

For enthusiasts Tof the hit ABC series Lost, it feels strange to think Benjamin Linus wasn’t there from day one. The show grabbed audiences immediately with its captivating mysteries. After a strong first season, its popularity only surged in the second year, largely thanks to Michael Emerson joining as Ben.

Through much of season 2, Ben posed as a captive named Henry Gale, tricking the main characters. The big reveal came at the season’s end: Ben was actually the leader of the mysterious ‘Others’ dwelling on the island’s hidden side. He had spent the season exactly where he intended—spying on the survivors. Ben’s complex morality, hunger for power, and sometimes deadly actions cemented him as a standout fan favorite.

8. Fin Tutuola: Law & Order: Special Victims Unit

Similar to Danny DeVito, Ice-T was already a famous face before he joined Law & Order: Special Victims Unit at the start of its second season. He plays Odafin “Fin” Tutuola, a sharp detective who moved to SVU from the narcotics division. Fin presents a tough exterior but harbors a deep commitment to helping victims of abuse and assault.

Initially partnered with the cynical, conspiracy-loving Detective Munch, Fin might have seemed like his opposite. However, many SVU fans believe their dynamic rivaled the chemistry between the show’s original leads, Benson and Stabler. Fin has now been a core character for 22 years, making him the longest-serving non-original cast member on this list. After Stabler’s departure in 2011, Fin became Captain Benson’s steadfast right-hand man.

7. Rafael Barba: Law & Order: Special Victims Unit

The Assistant District Attorney position on Law & Order: Special Victims Unit has seen many faces come and go. While Alexandra Cabot and Casey Novak were incredibly popular, Rafael Barba certainly challenged them for the title of fan favorite.

Played by Broadway actor Raul Esparza, Barba first showed up in the season 14 episode “Twenty-Five Acts,” joining later than anyone else on this list. He became a series regular the next season. Barba quickly became known for his sharp suits, strategic mind, and no-nonsense attitude. His wit, sass, and undeniable charisma won over audiences quickly. He was also the first male ADA to be part of the show’s main cast.

In 2018, Esparza left the show to return to the stage. His character’s exit in “The Undiscovered Country” sparked some debate among fans, but Barba has since returned for guest appearances in seasons 21 through 23.

6. Desmond Hume: Lost

Desmond Hume is easily one of the most intriguing characters from Lost, which is truly saying something. His very first appearance, revealing him inside the mysterious hatch from season 1, is considered one of the show’s most memorable moments. Though he appeared early in season 2, he vanished until the finale, becoming a regular cast member in season 3.

Initially, Desmond seems to have lost his grip on reality—not surprising after years of isolation believing the outside world was gone. As the show unfolds, we learn about his past and the touching love story with his wife, Penelope. His character takes center stage in the highly acclaimed season 4 episode, “The Constant,” often ranked by fans as one of the series’ best. Desmond’s journey is distinct from many others on Lost, and that uniqueness, combined with his kind and approachable nature, makes him a beloved figure.

5. Tommy Oliver aka the Green/White Ranger: Power Rangers

Mighty Morphin Power Rangers became a massive hit with kids in the mid-1990s. These five teens with martial arts skills and colorful suits captured imaginations everywhere. But the show delivered a shock in season 1, episode 17, by introducing an evil Ranger. Tommy Oliver arrived as the new kid, secretly under the control of the heroes’ arch-enemy, Rita Repulsa.

Tommy quickly gained popularity, not just for his cool looks and rebellious vibe, but because fans connected with his search for belonging. The writers crafted a compelling redemption story where Tommy breaks free from Rita’s spell and later becomes the leader, the White Ranger. His epic romance with Kimberly, the Pink Ranger, also added to his appeal.

4. Michonne: The Walking Dead

Michonne Hawthorne stands out as one of the most popular and formidable characters in AMC’s The Walking Dead. It’s easy for long-time viewers to forget that this katana-wielding warrior wasn’t part of the original group, even though she made a mysterious cameo at the end of season 2. She officially joined the main cast in season 3.

Initially, Michonne journeyed with Andrea, a character from the first two seasons. However, they separated when Andrea chose to stay in Woodbury, a community Michonne distrusted. Striking out alone, Michonne encountered Rick Grimes and his group. Though initially met with suspicion, she quickly bonded with Rick’s son, Carl, and eventually formed a deep relationship with Rick.

Played by Danai Gurira (also known for Black Panther), Michonne was a central character until the show’s 10th season. Her skill in combat is legendary, with a kill count often compared to Rick Grimes and Daryl Dixon.

3. Lexa: The 100

Few characters on this list caused such an uproar with their death that it nearly derailed the entire show. The 100, a post-apocalyptic teen drama on the CW (2014-2020), followed 101 young delinquents sent from a space station back to a ravaged Earth. While not a massive ratings hit, it cultivated a dedicated online fanbase over seven seasons.

In its critically acclaimed second season, The 100 introduced arguably its most iconic character: the warrior commander Lexa, portrayed by Alycia Debnam-Carey. Much like Ben Linus in Lost, Lexa’s introduction was deceptive. Initially presented as a humble servant, she’s revealed as the formidable leader of the Grounders, key figures in the first two seasons.

Lexa became the love interest of the show’s protagonist, Clarke. In season three, shortly after their relationship deepened, Lexa was tragically killed by a stray bullet intended for Clarke. This occurred partly because Debnam-Carey had been cast in AMC’s Fear the Walking Dead. The fan reaction was intense, leading to significant backlash, loss of viewers, and even sponsors. Though The 100 continued for four more seasons, it arguably never fully recovered its earlier momentum.

2. Spike: Buffy the Vampire Slayer

Buffy the Vampire Slayer remains one of the most celebrated supernatural teen dramas ever made. Conceived by Joss Whedon, it was a fresh take on his earlier movie of the same name.

In the third episode of season two, the show introduced Spike, a captivating, bleach-blonde vampire played by James Marsters. Spike burst onto the scene as a charismatic bad boy with a leather jacket and motorcycle. He was the polar opposite of Angel, Buffy’s brooding vampire boyfriend who possessed a soul. While Angel struggled with his nature, Spike embraced being bad.

Beneath the tough exterior, however, Spike was revealed to be a romantic softie with a love for poetry. His complex and often controversial relationship with Buffy continues to spark debate among fans years later. Spike became such a fixture that he not only stayed on Buffy for six seasons but also became a main character on the spin-off series, Angel.

1. Klaus Mikaelson: The Vampire Diaries

Topping our list is another vampire—or rather, a hybrid. The Vampire Diaries became instant must-watch TV for teens upon its 2009 debut. After a strong first season, the CW show elevated its game significantly in season two by introducing the Originals, the first family of vampires.

Klaus Mikaelson is the de facto leader of the Originals. Within the show’s lore, being an Original vampire means he’s far more powerful and harder to kill than typical vampires. While regular vampires could be dispatched with any wooden stake, Originals required wood from a specific ancient tree. Klaus further complicated matters by becoming part-werewolf, the first hybrid in this universe.

But Klaus’s appeal went beyond mere power. Portrayed by the talented Joseph Morgan, Klaus was more than just a dominant force; he was a complex, tortured artist fiercely devoted to his family. His immense popularity led to his own successful spin-off series, aptly named The Originals.

Adding new characters mid-stream is always a gamble for TV shows. Sometimes it backfires, but as these ten examples show, sometimes it introduces characters who become central to the story and absolute fan favorites. Their late arrivals didn’t stop them from making a huge impact.

Which late-addition TV characters are your favorites? Did they make our list? Leave your comment below!