Other mistake: The background action in the opening credits is slightly unsynchronized. This is most obvious at the "Goodbye gray sky, hello blue" line in the theme song, as Potsie mouths the lyrics. It's also obvious at the "My cycle hums" line, as the girl in the blue plaid skirt shows up at "cycle", rather than "my." (01:13:10)
Other mistake: June Lockhart is referred to verbally as 'The Honourable Judge McKay', but the end credits say 'Judge MacBride'.
Other mistake: The outside of the house does not match the interior setting at all.
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