Just as they start to sing "What Time Is It" the top of Troy's boxers are visible above his belt. He starts out wearing light colored boxers, which change to dark, then light, and again to dark colored boxers during this song.
Miley Cyrus has a brief cameo at the end of the film in the musical number "All For One". She is seen in a quick close-up, wearing a yellow top, dancing with other people on the rocks around the pool. Although this is commonly known to viewers of the Disney Channel, it is not as well known to those who rent the DVD, therefore this is valid trivia.