Board Thread:General Discussion/@comment-24021004-20170603011625/@comment-30064728-20170603022159

No one said that Bill destroyed all the 2D world; in fact, he destroyed his hometown and was stranded in the Nightmare Realm. Plus, he can only be a ghost-like demon in the mindscape before he could gain a physical body, so he retained he used to be. (In fact, even in the Weirdmageddon, Bill still be a triangle instead of a pyramid quite often, isn't it?)