It can be somewhat common among spinoff series or when cross promotion is desired, for characters from one series to appear in episodes of another series. This has most recently been seen in some of ...
I believe (but it is like fodder for another question) that Happy Days may be part of the largest spin-off tree in TV History (To the date of this posting) Is there a compiled list or graphic of the ...
Happy Days maintained a fairly realistic bent throughout it's run (I'm not here to debate shark jumping, I promise). Two notable detours from this were Mork and Mindy and Out of the Blue. Mork ...