For purposes of this list, "one-time" means they were central to an episode one time. Some of the characters listed here have appeared in later episodes, but only briefly. The characters are sorted by episode. Ms. Mellon ( Marcia Wallace ) Teacher at a school for gifted children that Bart is sent to after cheating on an I.Q Test. She is the only other character Marcia Wallace has voiced other than Edna Krabappel . [ 1 ] Cowboy Bob ( Albert Brooks ), owner of Bob's Roundup RVs. He has had non-speaking cameos after this episode, but made a brief speaking appearance in the season sixteen episode " Mobile Homer ", and is seen in the episode " Bart Gets an F ". [ 2 ] Jacques ( Albert Brooks ) is a bowling instructor who pursued an affair with Marge Simpson . Jacques has since made non-speaking cameos in subsequent episodes, such as " Homer and Apu " (in the MonstroMart's line of single, pathetic men who only pay cash for their groceries and do not chat with the clerk) and " Homer's Triple Bypass " (in the waiting room with his bowling ball stuck on one of his fingers). He makes a quick appearance on the bowling team 'The Homewreckers' in " Team Homer " losing to Homer 's team the 'Pin Pals'. He is also seen being startled by Bart on his skateboard (along with Bleeding Gums Murphy , Barney , Helen Lovejoy , Moe Syzlak ,