We just had a Pokemon party for our 3 year old. I modified and used alot of ideas I found here: Bingo, pokeball cupcakes...
For the invitations I scanned a picture of Pickachu into the computer and scanned in a photo of Ryan. Then I put Ryan's head on Pickachu's body. Underneath I wrote "Ryanchu". I wrote out all the party info of the back. It was cute. Another game we played in addition to Pickachu, pickachu, charmader and pin the bulb on bulbasuar was a pokemon scavenger hunt. I made three paper pokeballs for each child. On the back of each I put a pokemon sticker in groups of threes. Then I hid them all around the yard. The kids had to find 3 matching pokemon to win a prize. Trading was allowed and encouraged. They had a ball. Everyone had a great time.