To Beanie or Not to Beanie - S9-E12
Factual error: When Mr. And Mrs. Cunningham are talking to the Fonz in their bed about Joanie going to college, Mr. Cunningham is wearing a digital watch and those didn't exist in the 50s - 60s when the show takes place.
Answer: He was written off the series, never to be mentioned again as if he never existed. As a matter of fact, according to the final episode, he never did exist.
Rlvlk