Here is a simple activity my kids seemed to have really enjoyed. I have a very small 3rd grade class (15 students), but you can easily expand the game by adding more characters.
1. Hand out a character name card to each student.
2. Students must walk around and say "Hello, what's your name? My name is (Shrek)."
3. Because there are two of each character, students must ask around until they find the other student with a matching name card.
4. Change characters as many times as necessary.
Note: Boys loved the boyish characters, and girls the girlie ones (obviously). So an easy way to make them do this more than one round is to occasionally give them the characters they like less, so that they can hope to get one they like more next time.