Piderman somehow had people living in his basement, without knowing about it...
Pumkin's constant screaming after being carved means it probably hurt a lot. Likewise for slowly rotting to death.
Just whose blood did the Basement Monsters use for their cookie pie?
Baman and Piderman actually ate something that's recipe called for blood. Which was probably their own, giving how there's really no-one else around...
Baman wishes for Pumkin to be all better, at which point Pumkin grows a body. If being "all better" involves having a body, someone or something must have reduced him to a severed head before he was even introduced.