Sam's screen name ends with 818, the area code for the San Fernando Valley, where the movie takes place. Austin's online screen name ends with "609," the area code for the Princeton area, where they want to go.
Second time for Kevin Kilner and Chad Michael Murray to co-star. Kilner and Murray also co-starred in One Tree Hill, where Murray portrayed Lucas Scott and Kilner portrayed Peyton Sawyer's father, Larry.
At the dance Terry mentions "Austin Ames with the lady." "A devastating blow.." This would indicate that Austin should know that Cinderella is Sam, for Terry is obsessed with her and follows her around.
In Carter's first scene he is rehearsing a line for a role saying "anything is possible if you just believe." At the end of the movie he is in a comercial for the Believe acne cream and says "anything is possible if you just Believe"