Humphrey played a wolf who was a pet to Professor Bobo in the final host segment of Experiment 904 Werewolf. He is a dog owned by MST3k actor Kevin Murphy in real life and was apparently brought on the set that day the episode was filmed. Murphy also relayed in a 2004 interview with Too Much Coffee Man magazine that he scared Humphrey by accident while testing out his home movie theater speakers.
For a short time in 2008 on RiffTrax's official site, Kevin also submitted reviews under his other pet's Gumbo alias with the theme being on movies which had pets as co-stars. The selection included the likes of I Am Legend, which Gumbo gave one out of four paws due to the dog in that film not having a happy ending.