Great Uncle Stew is a supporting character in Stanley's Dinosaur Round-Up. He is the great-uncle of Stanley and Lionel Griff because he is the uncle of Mark Griff, but it is unknown which of his parents he is related to, or whether he is the widower of either parent's sister. He owns a dude ranch and owes money before Rockin' Rory converts it into a parking lot for an amusement park.
- This was John Ritter's final acting role as he passed away 3 years before the movie's release. The movie is dedicated to him.