Photo Credit: Steve Mack/FilmMagic
"Choose good underwear!" the actress, 31, jokes to iVillage exclusively. "I was kind of nervous about that."
Watch our exclusive video interview to find out why McAdams thought her first acting gig was her "one shot" to prove herself and why she used to beg for waitressing jobs.
Would you be willing to take your clothes off for a movie? Chime in below!