TV Shows That Turned One-Off Guest Stars Into Series Regulars

Making a TV show is a flexible process, and writers frequently change plots based on how well actors interact and what viewers think. Surprisingly, many beloved characters started as minor roles – intended for just one episode or to create a quick conflict. But when these actors made a strong impression, producers gave them bigger roles, turning them into series mainstays. The following examples show how a simple guest appearance can become a lasting part of television history.

‘Family Matters’ (1989–1998)

Jaleel White initially appeared on the show for just one episode, playing the pesky neighbor Steve Urkel. However, the audience loved him so much during filming that producers quickly asked him to return. Urkel quickly went from being a minor character to the main star of the show. His funny sayings and physical humor became more popular than the original story about the Winslow family. This change in focus completely reshaped the show and helped it stay on the air for many years.

‘Parks and Recreation’ (2009–2015)

Chris Pratt was originally hired for just six episodes as Andy Dwyer. The writers intended for him to be Ann Perkins’ short-lived, somewhat lazy boyfriend. However, the show’s creators quickly realized how funny and endearing Pratt was, and decided to make Andy a regular character. He eventually became a fan favorite, famously marrying April Ludgate, and his journey throughout the series became one of its most touching storylines.

‘Lost’ (2004–2010)

Michael Emerson initially joined “Lost” for three episodes as the character Henry Gale. However, his compelling and mysterious performance as Gale – later revealed to be Ben Linus – so impressed the creators that they changed the show’s overall story to make him a central figure. Ben Linus became a major villain, and eventually a complicated ally to the survivors. Emerson continued to play this key role throughout the entire series, earning significant praise and award nominations for his work.

‘Justified’ (2010–2015)

Originally, Walton Goggins was only meant to appear in the first episode of the show, with his character, Boyd Crowder, scheduled to die. However, early viewers really connected with the dynamic between Goggins and the show’s star, Timothy Olyphant. Because of this positive reaction, the producers decided to keep Boyd Crowder around and developed him into the series’ main villain. Boyd became Raylan Givens’ ideal counterpart, and this choice significantly deepened the show’s storylines and complexity.

‘The West Wing’ (1999–2006)

Initially, Martin Sheen was only contracted for four episodes a season as President Bartlet. The show’s creators envisioned the focus being on the White House staff, not the President himself. However, Sheen made such a strong impression in the first episode that the producers quickly realized he needed to be a central figure. He was immediately made a main cast member and appeared in every episode of the first season. From then on, the show largely centered on his presidency and personal story.

‘Stranger Things’ (2016–Present)

Honestly, I remember when Steve Harrington first showed up in ‘Stranger Things’ – he seemed like your classic, totally disposable high school jerk, the kind who’d be gone by the end of the first season. But Joe Keery was just so charming in the role! The Duffer Brothers clearly saw that too, and they wisely decided to give Steve a chance to turn things around. It was amazing watching him evolve from a pretty typical antagonist into this really protective, almost big brother figure for the younger kids. And his connection with Dustin? Forget about it – that became one of the best parts of the whole show! It was a really cool surprise, and it allowed the writers to do some surprisingly deep character development that I don’t think anyone expected.

‘Arrow’ (2012–2020)

Emily Bett Rickards initially joined the show for a single scene, playing an IT tech named Felicity Smoak. The producers and network immediately noticed a strong connection between her and the lead actor, Stephen Amell. Because of this, her part was quickly expanded from a one-time appearance to a recurring role, and then to a main character in the second season. Felicity became a vital part of Team Arrow and Oliver Queen’s main love interest. She added much-needed humor and brightness to the show’s dark and intense tone.

‘Supernatural’ (2005–2020)

Misha Collins first appeared in season four as the angel Castiel, initially for just six episodes. Introducing angels to the show brought a fresh and exciting element to the storyline, and viewers quickly fell in love with Castiel. He became a main character, joining Sam and Dean as one of the show’s three leads, and remained a vital part of the series for over ten years until it ended. Castiel served as a key supernatural helper to the Winchester brothers throughout their adventures.

‘Buffy the Vampire Slayer’ (1997–2003)

James Marsters originally joined ‘Buffy the Vampire Slayer’ to play the villain Spike for just a short time, with the character initially planned to die. However, Spike quickly became a fan favorite thanks to his rebellious style and sarcastic personality. Because of this popularity, Joss Whedon decided to keep him on the show. Spike evolved from a bad guy into an unlikely hero, became a regular cast member, and even became a love interest for Buffy. When ‘Buffy’ ended, Marsters continued playing Spike in the spin-off series ‘Angel’.

‘The Office’ (2005–2013)

Ed Helms first appeared on the show in its third season as Andy Bernard, initially as part of a storyline about merging the Stamford and Scranton branches. The writers hadn’t intended for his character to stay long, expecting him to leave once the branches combined. However, Helms fit in so well with the cast that he became a regular member of the Dunder Mifflin team. Over time, Andy worked his way up to become the Regional Manager, and his personality – including his musical abilities and struggles with anger – became a source of a lot of the show’s humor.

‘Law & Order: Special Victims Unit’ (1999–Present)

Ice-T initially joined “Law & Order: SVU” for just four episodes, filling in for another actor as Detective Fin Tutuola. However, his great on-screen connection with Richard Belzer led creator Dick Wolf to offer him a full-time position. Fin quickly became a beloved part of the show, eventually earning the rank of Sergeant, and is now the second longest-running character in the entire franchise. His real-world experience and sharp instincts proved vital to the SVU team’s success.

‘The Good Wife’ (2009–2016)

Alan Cumming initially joined “The Good Wife” for a brief role as political strategist Eli Gold, meant to assist Peter Florrick for only part of his campaign. However, due to strong positive reactions from both critics and viewers to Cumming’s performance and the character’s impact, Eli Gold became a regular part of the show starting in the second season and remained until the very end. He quickly became known as one of the show’s most interesting and captivating characters.

‘Scrubs’ (2001–2010)

Neil Flynn was originally hired to play the Janitor as a character only J.D. could see – a creation of his imagination. The plan was to reveal this at the end of the first season. However, Flynn was so hilarious during filming that the writers changed their minds and made him a fully realized character who interacts with everyone at the hospital. He quickly became a major rival for J.D. and a regular cast member, and his ability to improvise added a wonderfully quirky and funny element to the show.

‘Cheers’ (1982–1993)

Kelsey Grammer first appeared as Dr. Frasier Crane as a love interest competing with Sam Malone. Originally, the show’s creators intended to remove his character after his romance with Diane Chambers concluded. However, Grammer’s portrayal of Frasier was so strong that the writers decided to keep him on as a regular at the bar. He became a key part of the show’s cast for almost ten years, and the character proved so popular that it led to a successful spin-off series that lasted another eleven seasons.

‘Shameless’ (2011–2021)

Noel Fisher first appeared as Mickey Milkovich, a tough and often troublesome character, in the show’s first season. The connection between Mickey and Ian Gallagher proved popular with both viewers and the show’s creators. As a result, Fisher became a main cast member, and his character developed significantly. Over time, Mickey transformed from a violent criminal into a devoted husband and a fan favorite. His story of learning to accept himself became a central theme of the series.

‘The Big Bang Theory’ (2007–2019)

Melissa Rauch joined “The Big Bang Theory” as Bernadette Rostenkowski in season three, initially as a brief love interest for Howard. The writers didn’t plan for their relationship to become long-term, but Rauch’s unique voice and how well she played off Howard made her a great addition to the show. Because of her popularity, she was made a series regular in season four, along with Mayim Bialik. Bernadette then became a key character, juggling her work as a microbiologist with her family life.

‘Community’ (2009–2015)

Jim Rash first appeared on the show as Dean Pelton in a recurring role for the first two seasons. His funny entrances and outfits quickly became a fan favorite. Seeing how much comedy he brought to the show, the producers made him a main cast member starting with the third season. Dean Pelton then became a key part of the study group’s stories, moving beyond just being the school administrator. Throughout the series, a running joke was his strong infatuation with Jeff Winger.

‘Happy Days’ (1974–1984)

Initially, Henry Winkler played Arthur Fonzarelli as a supporting character with limited dialogue. Network executives were worried his tough look, especially the leather jacket, might be too much for viewers, so they kept his screen time short. However, Fonzie quickly became incredibly popular, soon overshadowing the show’s other characters. He became the central figure of the series and remained so for its entire run, ultimately becoming one of the most iconic characters in television history.

‘Glee’ (2009–2015)

Naya Rivera initially joined ‘Glee’ as a minor character, meant to simply be part of the ensemble in the glee club. In the first season, she had limited speaking lines and played a somewhat antagonistic role in the background. However, the show’s writers quickly recognized her talent for comedy and singing, and they gave her a much larger role. By the second season, Santana Lopez had become a main character with important storylines exploring her sexuality and drive to succeed. This character development was one of the most praised parts of the show.

‘Once Upon a Time’ (2011–2018)

Colin O’Donoghue joined the fantasy drama as Captain Hook, initially appearing in a multi-episode story as a villain meant to challenge the show’s heroes. However, audiences loved his charming performance so much that the writers changed his story. Hook became a romantic interest for the main character, Emma Swan, and evolved into a core hero who stayed with the show until the very end.

Tell us which of these character transformations surprised you the most in the comments.

2025-12-01 04:17