Most Helpful Guy
They were written by the same screenwriter, Diablo Cody, that's why they're similar.
It basically just snappy, sometimes witty, dialogue, and oddball situations. There isn't really any development to it, as in, no jokes build over time for a big payoff. Just a bunch of slang terms, and snarky one liners. Not saying that it's bad or anything (Jennifer's Body, as a film, was horrible) it just is what it is.