Helen Seinfeld of Seinfeld fame played nosy neighbor Raquel Ochmonek.
David Ogden Stiers of Mash fame appears in the "Turkey in the Straw" two-parter as a homeless man that ALF befriends.
Old Shame: None of the main human cast members had any major success after ALF, and all four actors playing the Tanner family have since retired (possibly as a result) from acting. Max Wright wanted nothing to do with the show for a long time afterwards, but later changed his mind, acknowledging in interviews how much joy ALF (the show and character) has brought to the world over the years.
Screwed by the Network: NBC promised that even if they canceled the show, they would make sure there would be an episode to resolve the Season 4 cliffhanger; they went back on that.