The only guest appearance on "Three's A Crowd" from a former cast member of "Three's Company."
Richard Kline appeared as his character, "Larry Dallas," from Three's Company (1976), in which he became very popular. This is his final appearance as the character.
Larry's party takes place in Apartment 201. This is the same apartment number that Jack, Chrissy, and Janet lived in in Three's Company.
Teresa Ganzel appears as "Greedy Gretchen", reprising a role she first played on "Three's Company" ("Lies My Roommate Told Me").