I think #4 is on the right track.
Witchiepoo (or Witchy-Poo, etc.) was the name of a character (who was a witch) on a pretty bizarre children's TV show called H.R. Pufnstuf that ran in the late 1960s and early 1970s.
I happen to be the right age to have it burned into my brain from back then, but younger people might well not have ever heard of it.
The line in the OP could be spoken by someone who was the right age to remember the show and character.
Discussions of the term online mention the show, e.g.
The show reeked* of late 60s psychedelia. The name "Pufnstuf" (name of the main character, a sort of dragon) was/is widely taken to refer to smoking pot ("puffin' stuff"). There are some representative video clips online.