The frog and a it's companion, a silly looking Woman Vampire are somehow tied in with William Castle and referred to as Castle Creatures on the boxes. The must not have been big sellers as the don't turn up often on secondary market.
There was also a greeting card depicting this design - I got it as a birthday card in 1966.Mike C.
I got it as a built hand me down and loved it. Mom liked to discard my stuff so no more.