Sometimes actors are unavailable—or hostile—for sequels, so rather than scrap their characters altogether, filmmakers find replacement stars and pretend that nothing changed.
Citing arguably the most famous instance of this, Katie Holmes was substituted for Maggie Gyllenhaal between Batman Begins and The Dark Knight, inspiring Redditor moopey to ask people to find other examples of actors getting swapped out for sequels with “no explanation.”
The entreat has garnered 300-plus responses, the highest upvoted of which mentions James Rhodes being played by Terrence Howard in Iron Man, and then by Don Cheadle throughout the rest of the MCU; Fandral being played by Josh Dallas in Thor and by Zachary Levi in the two sequels; and Victoria being played by Rachelle Lefevre in the first two Twilight movies, but by Bryce Dallas Howard in the third.
Other examples include:
Even though it’s a discussion about movies, Redditors couldn’t help but mention Aunt Viv’s original actor Janet Hubert being replaced by Daphne Maxwell Reid in The Fresh Prince Of Bel-Air. That show rivals Batman Begins/The Dark Knight for most memorable actor change.
It’s also worth noting that, although these replacements aren’t explained in their respective fictional universes, virtually every one has been explained by the actors and/or their directors.
Scheduling conflicts are a common reason, as cited by Zachary Levi’s frustrations at being in, out, in, and out of the MCU again, but others are due to pay, like Terrence Howard famously blasting Marvel for failing to deliver on the promise of an increased salary for Iron Man sequels.
It turns out having no explanation is much more pleasant.