Mr. Mendelbaum (voiced by Larry Storch) is a comic book publisher.
He once considered Jon's ideas for a new comic book. He was unimpressed with everything Jon had proposed, especially "Buddy Bear", due to his dislike of bears.
Later, upon overhearing the remark: "I'm glad we got rid of that stupid-looking bear", Garfield (as the Caped Avenger) assumed that Mendelbaum was the one who stole Pooky. Garfield then attacked Mendelbaum, persisting until Jon gave back Pooky (who had actually been cleaned the whole time).
As Jon apologizes for Garfield's antics, Mendelbaum tells Jon that he likes the idea of a "crime-fighting house pet"- namely Odie (as Slurp). Jon accepts the idea, much to Garfield's dismay.