Great points R4Don4. Yeah, maybe go with Don's suggestion instead.
Treat John Ratzenberger like your bitch and personal play thing while he's at your work, after all, he signed up for that when he decided to be an actor and he'll never be coming back to your work again. What kind of story is he doing about your company for Made in America? Oh well, it probably doesn't matter. I'm sure he'll find fan boy antics "cute", and how could your actions possibly effect the way they edit their story about your company? If your boss asks about your behavior, just explain that your online buddy R4Don4 said it would be okay, because when will John Ratzenberger, er, "Cliff Claven" ever come to your work again?
Here's an idea; if John Ratzenberger won't hold the Creature Cantina sign, wait for him to go into the restroom at your work. Then go in and wipe your ass with the sign and use the feces to stick it on him. Be sure to take some pictures of him going to the bathroom, and with the sign stuck on him. You could post them here, or sell them to the Enquirer. After all, "actors are attention hungry ego maniacs, he will love it".
Can't wait to see that sign indeed.