I loved Mork & Mindy as a kid.
I remember him being on Good Morning America in the 80's, and he went on one of his crazy episodes around the set, stumbled onto the kitchen part of the set (I'm leaning to remember he went into a Julia Child impersonation) He then opened the fridge, where the camera couldn't see inside, gasped, exclaimed "Jimmy Hoffa!", and quickly shut the door. I don't know why I remember that particular instance of his wonderful craziness, but I do.
Prayers for his family and friends.