It does take a lot from the first film and re-use it in a slightly different way. Actually, it does that a lot. Another missing night, another day spent reconstructing the forgotten events. They were drugged by the same guy. When they woke up, one of them was missing (again) and they needed to reconstruct the night in order to find him. Once again, it turned out that the things they got up to had absolutely nothing to do with where he was, though this time they hadn't put him somewhere and forgotten. The first place they checked was the roof, actually.
Instead of losing a tooth, the dentist wakes up with a ridiculous tattoo on his face, and instead of marrying a stripper, he proposes to one, is turned down and sleeps with her in the back room of strip club, only she turns out to be a he. The guy who drugs them makes another very bad speech, the baby is replaced by a drug dealing monkey, and they steal a Buddhist monk rather than a lion.
As in the first film, they get back in time for the wedding, and everyone appears to live happily ever after. There is even an appearance by Mike Tyson.
I kind of got the feeling I was watching a re-make of the first film with a few details changed rather than something new, but that was okay because it was still funny. Probably won't get the DVD though, and definitely won't be going to see it again at the cinema. But still, not that bad!