"Arthur, Arthur"

This is a potentially interesting idea but tonally odd, especially that tag.  I'll go with a C+.

Notes:

• Fonzie's half-brother by his now late father Vito is also named Arthur.  He lives in San Francisco, so I imagine him running into Richie.
• The episode where Vito brought Fonzie a kimono without identifying himself is referred to, a nice touch.
• Marc Flanagan and Craig Heller didn't write any other HD episodes, so that might explain a bit why this episode feels different than others.
• At the time of breakup, Chachi said he didn't want to be friends with Joanie, but we hardly see them hang out with anyone else at this point.