Prev 15 of 24 Next
15. Tom Welling in 'Smallville'

While it's not crazy to see a 24-year-old play 18, Tom Welling was supposed to be playing a 14-year-old version of Clark Kent when Smallville made its 2001 debut. That first episode becomes particularly absurd when the 6'3" Welling openly worries about starting his freshman year of high school.