Richard Harris played Hogwarts Headmaster Albus Dumbledore for the first two Harry Potter films before he died in 2002. Michael Gambon replaced him for the remainder of the series.
Alessandra Torresani to Mae Whitman
The role of Ann Veal (her?) in “Arrested Development” was originally played by Alessandra Torresani in Season 1 before she was recast with Mae Whitman for the second season and beyond.
Lecy Goranson to Sarah Chalke
Lecy Goranson originally portrayed Becky Conner on ABC’s “Roseanne” but opted to leave the show to focus on school, and Sarah Chalke was brought in for Seasons 6 and 7.
In a bizarre turn, Goranson wanted to return for Season 8 but couldn’t appear in some episodes, so the show used both her and Chalke throughout the season. Chalke became the sole Becky Conner in Season 9.
Bruce Banner/The Incredible Hulk
Edward Norton to Mark Ruffalo
Despite a well-received stint as the Jade Giant, Edward Norton and the studio didn’t see eye-to-eye on parts of the character, and he was recast with Mark Ruffalo for the character’s next appearance in “The Avengers.”
Jodie Foster to Julianne Moore
After winning an Oscar for her role of Clarice Starling in “The Silence of the Lambs,” Jodie Foster wasn’t able to reprise her role for the sequel. Julianne Moore was brought on for “Hannibal.”
Ed Skrein to Michiel Huisman
Ed Skrein portrayed Daario Naharis for “Game of Thrones'” third season and then chose to step away when he was cast in the lead of “The Transporter: Refueled.” Michiel Huisman came in to play the mercenary for Season 4 and beyond.
Rachel Weisz to Maria Bello
After two adventures as Evy in “The Mummy” and “The Mummy Returns,” Rachel Weisz decided not to return for “The Mummy: Tomb of the Dragon Emperor.” Maria Bello stepped in to take over.
Josh Dallas to Zachary Levi
In a weird case of happenstance, Zachary Levi was originally cast to play Fandral in “Thor,” but wasn’t able to fit it into his schedule while shooting his NBC series “Chuck,” and Josh Dallas became his replacement.
However, when the time came to shoot “Thor: The Dark World,” Dallas was busy shooting his ABC show “Once Upon a Time” and the role went back to Levi.
James Rhodes/War Machine
Terrence Howard to Don Cheadle
Terrence Howard claims he was pushed out of the role of War Machine following the first Iron Man film by Robert Downey Jr., but whether or not that’s true, he was replaced with Don Cheadle, who has played the character across multiple MCU films ever since.
Claudia Wells to Elisabeth Shue
After playing Marty McFly’s girlfriend Jennifer Parker in the first “Back to the Future” film, Claudia Wells chose not to reprise her role so she could take care of her mother. Elisabeth Shue was cast for “Part II.”
Lisa Robin Kelly to Christina Moore
Lisa Robin Kelly appeared throughout the first five seasons of “That ’70s Show” before being forced out by producers due to her issues with substance abuse. She was replaced by Christina Moore.
Unfortunately, Kelly died of a drug overdose in 2013.
Katie Holmes to Maggie Gyllenhaal
After playing Rachel Dawes in Christopher Nolan’s “Batman Begins,” Katie Holmes chose not to return to the series and Maggie Gyllenhaal was cast for “The Dark Knight.”
Ross Butler to Charles Melton
After appearing in Netflix’s breakout hit “13 Reasons Why,” Ross Butler decided not to return to the CW’s “Riverdale” in the role of Reggie Mantle and the part was recast with Charles Melton.
Andy Whitfield to Liam McIntyre
Andy Whitfield played the titular character for the first season of Starz’s “Spartacus.” Before the second season could begin shooting, Whitfield was diagnosed with cancer. Starz decided to shoot a prequel series without Spartacus following Season 1 — believing that Whitfield would recover.
The actor died in 2011 and the role had to be recast, with Liam McIntyre playing the character.
Conan Stevens to Ian Whyte to Hafþór Júlíus Björnsson
The role of the Mountain in “Game of Thrones” has been a bit of a revolving door throughout the series. Conan Stevens played the character in Season 1, Ian Whyte took over in Season 2, and Hafþór Júlíus Björnsson has been playing the part since Season 3.
Rachelle Lefevre to Bryce Dallas Howard
The role of the villainous Victoria in the “Twilight” saga was played by Rachelle Lefevre for the first two films before Summit recast the role to Bryce Dallas Howard in “Eclipse.”
Janet Hubert to Daphne Maxwell Reid
After three seasons as Aunt Viv on “The Fresh Prince of Bel-Air,” Janet Hubert was removed from the series after reported disputes with NBC and not getting along with Will Smith. Daphne Maxwell Reid was brought in as the new Aunt Viv.