Brent Spiner, Star Trek: The Next Generation
Data is everyone's favorite android... Except for Brent Spiner, apparently. Spiner has played Data for all seven seasons of the show and four TNG movies. He already has a great career outside of Star Trek but doesn't think that he can go back for another round. Data isn't supposed to age, after all.
"I mean, there was just a finite amount of time that I can actually play Data, no matter what anyone says. So many people were like, 'Oh, you can do it. You're not too old,' and then I do it and they go, 'You're too old. Why'd you do it?" he told TV Guide. "I think we did it in such brief sequences that it was fine to do it and I felt good about it. but I wouldn't really entertain the idea of doing it again because I just don't think it would be realistic."