This is kind of an obvious one, but it's only as we viewers age that the actors playing Danny, Sandy, et al., start to look that bit older too. One of the original incarnations of the show was framed by a high school reunion, which meant casting older actors made total sense. And, if Rizzo and the rest of the Pink Ladies kicked off Grease stood in the gym surrounded by "Welcome Back, Seniors" banners, their ensuing conversation in the parking lot would make much more sense too. In flashback, it's fine. 

As it stands, the ladies' discussion of what it means to be high school seniors is slightly cringe-worthy. The Independent did a "Where Are They Now?"-style piece about the cast back in 2016. The most shocking thing about the collection of photos is that nobody looks too different to how they did in the movie. This is either down to good genes, plastic surgery, healthy living, or the fact that none of them were all that young to begin with. For clarity, the year Grease was released, the youngest cast member was John Travolta at 24. Stockard Channing was 34, Jeff Conaway was 28, and Olivia Newton-John was 30.