Me: Reference Desk, can I help you?
Patron: Can you ask Wicked Peter what his real name is?
Patron: H.R. Pufnstuf
Patron: What is H.R. Pufnstuf's real name? What does the H.R. stand for?
Holy smokes. I search Google for just "h.r. pufnstuf" and the first first result was a Wikipedia entry (ah-ha, Wicked Peter = Wikipedia, so that's one mystery solved).
That article, along with a few other websites I checked, said the H.R. stands for "Royal Highness" (backwards - or "His Royalness"), according to the shows creator, or "hand rolled" (a pot reference), according to its fans.
I never watched this show, so I don't know about the pot reference. But since this was about the same time as Puff the Magic Dragon, I guess people making that sort of connection isn't surprising.
Anyway, I told the patron that it stood for His Royalness, but other people thought it stood for other things. That must have been enough, and the patron said thanks and hung up.