The Ballad of Joanie and Chachi - S11-E2
Visible crew/equipment: After Chachi walks out of the college classroom, when Joanie takes a seat and starts crying the boom mic dips into view at the top of the screen, in the wideshot.
Visible crew/equipment: When Fonzie and Chachi are wearing their tuxes, Chachi nervously picks up the telephone for no reason, and just as he walks around the table we can see set lighting at the top of the screen, over the window.
Answer: When it was originally broadcast there was a different ending. A new ending was added when the show was rerun to set up the Mork and Mindy series.