Three's Company: Larry's Sister

Three's Company: Larry's Sister
ABC
January 11, 1983
Sitcom
DVD
C

Paul Wayne's story about the title character, 19-year-old Diane, suffers from de ja vu and is weaker than its predecessors.  When Jack joins the girls at aerobics, it's a pale memory of the yoga practice in (I believe) Season Two.  And comparing this episode to the one about Janet's sister, there are the following flaws:

• Larry is less plausible as an overprotective sibling than Janet is, although I suppose it's comparable to Howard Borden being overprotective of his younger sister on The Bob Newhart Show;
• The set-up is more contrived, in that of course Janet's sister would stay with her, but Larry has to ask for Diane to say since he has a small place (a studio I think);
• Jack literally went to bed with Jenny Wood, while here he's just out on a late date (grunion-running), so he's not "caught" even kissing Diane Dallas;
• Janet got pissed off but she didn't sock Jack without letting him explain, as Larry does here;
• Even after Diane tells Larry the truth, he doesn't believe her, unlike Jenny, who had a "So what if something happened?" attitude;
• There's nothing comparable to Chrissy's Gracie-Allen-ish story that helps Janet see that she's been unfair to Jack and Jenny;
• In the tag, Diane gives Jack an affectionate but not lewd goodbye, and Jack's roommates are ready to jump to conclusions again.

This is one of those episodes where I really feel sorry for Jack.  And no offense to Lucinda Dooling, who gives a nice performance as Diane.  I just wish the writing was better.