|This needs a stretch.|
Theodore Jones (called Grampa Teddy by Fred), is a movie actor.
He looks quite a bit like Fred, but with white hair and a small mustache. Just like Fred, he wears a white shirt with a blue collar, and a red ascot (Fred says he got his fashion sense from his grandfather, along with the idea of monster-hunting).
Insert details here.
Scooby-Doo (DC Comics)
He was holding a film festival with the newly-found and priceless master print of Return of the Monster Hunter, when it was stolen and movie monsters showed up. (Legend of the Silver Scream)
Insert details here. (Sound Stage Spook)