In the PowerPuff Girls one of the strongest villains they face is Him, but his appearance, name, and voice are quite confusing. Who and what is Him?
HIM is the Devil.
From the Wikia page:
It is implied that he is the devil himself, or at least some form of demon, in The Powerpuff Girls series, he is said to be "so sinister, so evil, so scary, so horribly vile that his real name can never be said, lest fear be struck into the very hearts of men."
His voice and mannerisms were inspired by the Chief of the Blue Meanies in The Beatles movie "Yellow Submarine".
His physical appearance is an amalgamation of sorts, borrowing a mix of concepts and imagery in regards to Satan with cross-dresser attire.