This is the unrated version of this film and also the third movie that they created. This isn't the type of movie where you HAVE to see the first two first, but it helps you get to know the characters.
In the movie Jim and Michelle have graduated college and Jim proposes to Michelle. Of course she says yes, otherwise we woudn't have a movie. The problem is that (and you know this if you've seen the other movies) Jim seems to mess everything up...a lot! It is part of what makes the movies all so funny. They are a bit over the top and I can't imagine anything like this happening to anyone I know, but still.
Like I said, it's just really funny and you have to excuse the nudity and bad language. If you know anyone who is getting married and they have a fun and great sense of humor you should have them watch this. It's hilarious!