Sitcoms copied each other. This same premise (of one character picked for modeling, then turning into a huge disappointment) was later redone by: Diff'rent Strokes: The Model (1981); "Who's the Boss": Model Daughter; The Nanny: Maggie the Model (1994). It might have originated even earlier than here. This is the only sitcom known to have used a man---and an older one at that!---instead of a young girl.
This episode was co-written by series star Pat Harrington, Jr., who portrays Schneider, the building superintendent.