Trivia: When Frenchy and Doody arrive at the National Dance Off, Frenchy asks Doody how does she look, to which Doody replies, "Like a beautiful blonde pineapple." Barry Pearl (Doody) ad-libbed this line.
Trivia: The rest of the cast did not see Olivia Newton-John in her greaser girl outfit until she walked into the scene at the Graduation Carnival. The stunned reactions of the T-Birds are real.
Trivia: Leo's name is never spoken in the movie. It is only mentioned in the end credits.
Trivia: Jeff Conaway (Kenicke) and Olivia Newton-John (Sandy) were brother-in-law and sister-in-law in the early 1980s. Conaway was married to Olivia's sister Rona.
Answer: Watched that scene again now and I just think it was poor writing (in what's still a classic film regardless). How none of the judges noticed that Cha Cha took another girl's (Sandy's) place even after she'd already been "tapped out" is another huge plot hole. Plus a lot of people in America were watching the dance on TV and it's not mentioned by anyone after this scene. 35 years later and that scene still bugs me (haha).