Well, I guess it's not really a cameo, but here happens to be a kid dressed up as Sonic in the movie. It's in the scene where the 3 witches were on the streets on Halloween night, shortly after a little girl in an angel costume says "God bless you", and one of them screams. It's best seen when you look to the very left. I'll try and get a screenshot later.

Excardon me if this is already on the SSN Wiki.