The small boy in question is a over-energetic boy who happens to be quite clumsy. Whenever he runs into things or hurts himself, he gets right back up and just goes back to what he was doing. I want his 'uncle' (distant relative) to give him a nickname, something to the point of 'juggernaut', 'indestructible', 'unstoppable' because this kid nearly knocks himself out constantly by running into objects before his parents can ever stop him in time. The uncle has a weird, morbid sense of humor, can be a real sadist, and is a novelist if that helps.
So I need a silly male nickname in Japanese for young, rambunctious boy. (The boy's name is Katsu if that helps too.) Any suggestions for names or websites for nicknames would be a really big help.
EDIT: Fixed small problem.