It opens with Zac Efron in high school and he is the high school stud. Basketball star, nice guy, and has hottest girl in school for his girlfriend until she tells him that she's pregnant right before he plays his biggest game ever with scouts in the crowd...what does he do? He follows her out and doesn't play his game and they live happily ever after, right? No.
Jump ahead 16 or so years and we have Matthew Perry stuck in a deadend job with two teenage kids who don't respect him, and on the verge of a divorce. He goes to stay with his high school buddy who's super rich and is also the biggest Star Trek nerd ever. When he wakes up the next morning he's 17 again! He re-enrolls in high school, tries to befriend his own kids, and ends up trying to get back together with his wife (all while still 17!).
It's a lot like Big or 13 Going on Thirty with lots of chances for comedy and lots of opportunities for growth and reflection. I really enjoyed this movie. It was smart and funny and a great family film.