His ghost form kind of resembles his deceased adoptive father Luke Montgomery.
It's revealed in the episode A Bad Day for Craig, that eating will keep him happy. If he goes too long without eating, he will have an unlucky day and have a grumpy look on his face. If he goes without food any longer, he will turn into a huge angry monster and raid the city.
He has an infinite digestive system, meaning he can eat as much as he wants without feeling full or sick.
Craig's laser guns have nine colours on them and each one has a different ability.
Red: No special ability. Just normal red lasers.
Yellow: Craig will become invulnerable if he shoots himself.
Cyan: Freezing things in solid ice.
His birthday is June 2nd.
This means his birthstone is a pearl, just like Stephanie.