In the movie "High School Musical", Ashley Tisdale really does play the role of Sharpay.
The director says to Maddie that "We're All In This Together", which is one of the songs in "High School Musical."
Maddie says "Push It To The Limit" in this episode. That is a song by Corbin Bleu, Ashley Tisdale's (Maddie) co-star In High School Musical, and High School Musical 2.
Maddie says in this episode, "...and I don't look like Ashley Tisdale?" Ashley Tisdale is the girl who plays Maddie Flitzpatrick in real life. So, she is referring to herself.
When London and Maddie are doing "Bop to the Top", Maddie yells at London to sing, and London says she doesn't wanna make a fool of herself in front of her daddy, however the lines are portrayed like they were never picked up by their stage mics, but normally wouldn't if something was said like that wouldn't it be picked up by them.