1.Andy Dwyer was only supposed to appear in six episodes of Parks and Rec before Ann kicked him to the curb, but Chris Pratt was "too funny to not use," according to the show's creator Michael Schur.
2.Gunther, the iconic bleach-blonde Central Perk barista, was promoted to a supporting role on Season 2 of Friends despite originally being just a background character.
3.Jesse Pinkman was supposed to die in the Season 1 finale of Breaking Bad, but creator Vince Gilligan flipped the script and kept him around for the show's five-season run.
4.Summer Roberts was intended to be a guest-starring role on The O.C. However, Rachel Bilson nailed the part and was bumped to a series regular before the end of Season 1.
5.Andy Bernard was only supposed to appear in an eight-episode arc as the cocky antagonist on The Office. Writers had so much fun crafting stories for Ed Helms that he became a series regular in 2007.
6.Topanga Lawrence was supposed to be Cory's hippie classmate in a few episodes of Boy Meets World, but her character became too popular to write off.
7.Despite serving as the show's protagonist for six seasons, Jack Shephard was supposed to die in the pilot of Lost.
8.Dr. Frasier Crane was only meant to appear in a few episodes of Cheers. However, Kelsey Grammer's acting chops earned him a series-regular position in addition to a spinoff that lasted 11 seasons!
9.Dr. Arizona Robbins was given a three-episode arc on Grey's Anatomy, but she stuck around for seven seasons!
10.The diner owner in Stars Hollow was originally written as a female character named Daisy on Gilmore Girls. When creator Amy Sherman-Palladino received a note to add more men to the series, Scott Patterson was cast instead as just a guest star. His chemistry with Lauren Graham’s Lorelai Gilmore was so strong, he became her primary romantic interest on the series.
11.Bedelia Du Maurier, Hannibal Lecter’s psychiatrist, was written as a cameo for Gillian Anderson on Hannibal, but writers were inspired by Anderson's performance and Bedelia became a series regular in Season 3.
12.Steve Urkel was only supposed to appear in one episode of Family Matters, but audiences wanted to see more of the Winslows’ nerdy neighbor, so Jaleel White was cast as a character on the series.
13.Felicity Smoak was intended to appear on one episode of Arrow. Yet her role was quickly expanded as she became the primary love interest for Oliver Queen.
14.President Bartlet was supposed to be a supporting role, only appearing in four or five episodes per season of The West Wing. Yet Martin Sheen played the commander in chief on Aaron Sorkin's political drama for seven years.
15.Detective Odafin Tutuola, played by rapper Ice-T, was only meant to be on four episodes of Law & Order: Special Victims Unit. Thankfully for fans of the show, Ice-T has appeared in 474 episodes and is still going strong!
16.Dr. Camille Saroyan was supposed to be killed off after a small story arc on Bones, but she ran the Jeffersonian lab for over 200 episodes!
17.The Cigarette Smoking Man was meant to be a background role on The X-Files, but he quickly became the main antagonist to Agents Mulder and Scully.
18.Colin O'Donoghue was hired to play Captain Hook for four episodes of ABC's Once Upon a Time. His chemistry with Jennifer Morrison's Emma Swan was unmatched, and he was written in as a series regular.
19.The Tipton Hotel's lovable bellhop, Esteban Julio Ricardo Montoya de la Rosa Ramírez, was only going to appear in a few episodes of The Suite Life of Zack and Cody, but he was promoted to a series regular after his successful performance in the episode “The Ghost in Suite 613.”
20.Coconut Head wasn't supposed to have lines on Nickelodeon's Ned's Declassified School Survival Guide. Yet he became a fan favorite and stayed for the duration of the series.
21.The Janitor on Scrubs was a small role intended to be a figment of J.D.'s imagination, but as the show got picked up for more seasons, creator Bill Lawrence dropped that storyline and promoted Neil Flynn to a series regular.
22.Stacey Dillsen, the Pacific Coast Academy student with a notable lisp on Zoey 101, was only supposed to be in one episode, but execs loved her and she stayed on for 30 more!
23.And finally, Misha Collins signed on to play Castiel for three episodes of Supernatural but ended up spending 12 years as the trench coat–wearing angel.
