When I was a kid, the closest I ever got to decorating my own cake was a cookie and a little tube of gel icing. I had plenty of fun with just that. Imagine how awesome it would have been if we had edible paper back then? I can't say I'm not a little jealous of kids these days.
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.
Everyone knows that corgis are the BEST dogs in the world. NO ARGUING! It's the absolute truth! Combine the best dog ever with what may be the best dessert ever and let's all be careful, we don't want to be dividing by zero here.