Dawson Casting: Many of the actors were actually in their early 20s, though when the films initially started, most of the characters were played by people close to their actual age. Taylor's actress, Monique Coleman, was 26 at the time of the first film.
Averted by Austin Butler in the spin-off film, who was nineteen and playing a college freshman.
In English, FPS fans will lose their minds when they realize that misanthropic Sniper is teaching high school kids.
I Want You to Meet an Old Friend of Mine: Prior to the first film, Olesya Rulin (Kelsi) and Lucas Grabeel (Ryan) had been in Halloweentown High together, as Natalie the troll and Ethan the warlock, respectively.
Incestuous Casting: One character remarks that if Sharpay could find a way to play both Romeo and Juliet, Ryan would be out of a job, suggesting that the two have played romantic partners in the past.
Romance on the Set: Between Zac Efron and Vanessa Hudgens, who were together for over five years. They confessed to liking each other during the first film and got together during the second. (Although they hid it for as long as they could to avoid media attention). Kenny Ortega admitted that he'd noticed their chemistry since the beginning, and deliberately paired them during auditions.