These actors played their characters so well, they could never play another role.

1. Sean Astin, who played Rudy in Rudy

2. Jim Parsons, who plays Sheldon Cooper in the Big Bang Theory

3. Every single actor It's Always Sunny in Philidelphia

4. Huge Laurie, who played Gregory House in House

5. Neil Patrick Harris, who played Barney Stinson in How I Met Your Mother

6. Aubrey Drake Graham, who played Jimmy Brooks in Degrassi: The Next Generation

7. Daniel Radcliffe, who played Harry Potter in the Harry Potter series

8. Michael Richards, who played Kramer in Seinfeld

9. Leighton Meester, who played Blair Waldorf in Gossip Girl

10. Zach Braff, who played John Dorian "JD" in Scrubs

11. Hillary Duff, who played Lizzie Mcguire in Lizzie Mcguire

12. Sarah Jessica Parker, who plays Carrie Bradshaw in Sex and the City

13. Miley Cyrus. Miley Stewart/Hannah Montana on the Disney show Hannah Montana

14. Michael J. Fox, who plays Mary McFly in Back to the Future