A (phonologically perfect) pun on toad (the creature) and towed (PST/PSP of the verb tow, as in the parking sign VIOLATORS WILL BE TOWED), put together via the image of a wicked witch turning a parking violator (possibly a prince) into a toad.
This particular pun was a favorite of the comedy group Firesign Theatre, in the routine “Toad Away” — first recorded on 12/9/70, then appearing as the first track on the 1972 compilation album Dear Friends and on at least two later compilations (Forward Into the Past in 1976 and Shoes for Industry: The Best of the Firesign Theatre in 1993). The audio from Dear Friends:
This is framed as a sermon, with the hymn “Toad Away” sung to the Christmas carol “The First Noël”. The video accompaniment has a series of images — religious images, signs, photos of cars being towed, and of course of toads, plus this wonderful sign, whose punning is presumably inadvertent:
(Photo taken by Nolan Tanner 9/30/06 at the TACA Fall Craft Fair at Centennial Park in Nashville.)
If I park on the grass, will the park police give me a toad?