Romeo & What's Her Name

Understudies never get to perform

. . . which is why being Juliet's understudy in the school's yearly "Evening with Shakespeare" is the perfect role for Emily. She can earn some much-needed extra credit while pursuing her main goal of spending time with Wes, aka Romeo, aka the hottest, nicest guy in school (in her completely unbiased opinion). And she meant to learn her lines, really, it's just:
a) Shakespeare is HARD,
b) Amanda, aka the "real" Juliet, makes her run errands instead of lines, and
c) there's no point because Amanda would never miss the chance to be the star of the show.

Then, Amanda ends up in the hospital and Emily, as the (completely unprepared!) understudy, has to star opposite the guy of her dreams. Oops?