Arson

Arson isn't his real name and the only reason he refuses to say it is because he enjoys seeing people be bothered by it;
Peppy guy, barely ever seen not smiling;
Is, in fact, an arsonist;
Often bothers Cornchip just to try to get a reaction out of him that isn't an uninterested hum or a snarky comeback;
He's actually very intelligent but he loves messing with Cornchip, and almost gets them caught every time;