No movie surprised me more in 2012 than “21 Jump Street”. You heard that they were rehashing this teen cop drama from the 80s, and you groaned. You heard it starred Channing Tatum, and you groaned. You saw that it co-starred the new, weirdly skinny Jonah Hill, and some of your groaned again. But somehow, some way, “21 Jump Street” is the funniest movie of the year. I’m as shocked as you are. The movie walks a tightrope of being self-aware without being obnoxious, and pokes fun at the source material, but in a warm, appreciative way, cleverly playing with the conventions and stereotypes of teen movies. The jokes are shrewd, and “21 Jump Street” is a raucous ride from beginning to end.