http://www.ravelry.com/patterns/library/pokeball-hat I also used the same basic pattern on the mitts.
I also found that if you are staying up late you may make two mitts for the same hand. But that was easy to fix I frogged back to the thumb and reknitted. Not a big deal
At this point I am working on a double knit scarf for him as well that will incorporate the same Pokémon ball on the end and have Pokémon in the center. Trying a new method of double knitting so will see how it works out.