You really can't go wrong with a classic comic book POW or SMASH or BOOM for a little boy's birthday cake. Toss in a maniacal Joker spreading mayhem and you've hit the optimal level of chaos and fun to get the party going.
I'm not a huge fan of having a face in the bathroom watching me, but this robot is so neutral and all about business. You know he takes his job seriously because he is programmed to do one thing and one thing only, provide you with fresh clean paper. Thanks robot!