Theobromine sorta is, actually. You'd just have to eat an awful lot of Lindt bunnies in a very short period of time. Or... actually, I doubt you could eat enough milk chocolate bunnies to do it, you'd have to ingest your theobromine in the form of raw cocoa. I don't know why you'd do that, but you could if you wanted to. (At least in theory. As the article points out, one of the early effects of theobromine poisoning is vomiting, not that you probably wouldn't already feel queasy from all that chocolate.)