Spoiler alert.
I don't think I need to go through the whole story, as you might already have heard that elsewhere. What I would like to get u excited about is probably something u didn't foresee. You all know that scene from the trailers where shrek gets puked upon by a creature in a pram... That pram has an ogre baby. Yeah! That was the potential spoiler. Fiona tels shrek that she's pregnant and that he's about to become a father. And as you'd expect, shrek is not ready. yeah yeah, the typical concern, whether I will be a good father for my children or not... but in his case, its different because he's an ogre. He is worried his kids will be ashamed of calling an ogre their father. I really felt for that poor guy in the particular sequence where he's talking to donkey about it.
Oh, almost forgot, before this talk, there is a nightmare sequence which involves hundreds and thousands of little ogre babies just gushing into his house. It starts off with the one in the pram. And lemme tell you, he's really CUTE. they did a really nice job on the character design and modeling. Then there are 3..5..8...15... and so on. They are destroying the house, getting themselves into trouble and all that. Kinda reminds me of the tom and jerry episode where tom is baby sitting a baby. LOL. Then the number just 'explodes'! They are coming in from the windows, the door, chimney(huh?) etc. I wonder how much computing was required for rendering that crowd of detailed babies. Great job there!
Then the puss and donkey being changed into each other is just a gimmick and lends itself to a few gags in the movie, but it doesn't have any solid purpose like donkey turning into a steed in the second movie. But it can easily be ignored. The rest of the movie is really funny. I was laughing from the first scene to the last dance sequence. Even the death of the frog kind sequence was comic! Other sequences that I really liked include the fateful events that happen on th day shrek and Fiona are filling in for the kind and queen. Some of them you've seen on the tv, but there is a big shot that they are keeping reserved for the movie only. so don't miss it, GO WATCH IT!