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. Humphrey had previously appeared in each of the author photos in The Amazing Colossal Episode Guide.
Kevin 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.