Thanks to Lucy Chase Williams, I was alerted to a large cel picturing Vincent Price as Vincent Van Ghoul embraced by Scooby-Doo. The cel is inscribed "To Ry Pal Rincent, Scooby" followed by a paw print. The cel came from the Los Angeles area and is clearly not a seri-cel. I suspect it may have originally been created as a personal memento given to Vincent Price for participating in THE 13 GHOSTS OF SCOOBY-DOO, but there is no such provenance attached... but for what other reason would a cel like this be inscribed "To Ry Pal Rincent"?