After the big dance number at the beginning the camera follows Diana. If you look, the dancer that looks like John Ritter and says, "I've never been cut this soon" is standing behind her.
In the last number where they all dance, watch the right hand bottom corner. As they all do their high kicks we see one dancer (I believe a male) fall and then pop back up and continue dancing. Look very closely.
During 'Hello Twelve Hello Thirteen', Diana says hello thirteen then hello twelve.
When Paul falls and is taken to hospital, Diana tells him she has his dance bag and runs to give it to him. However, as the the final cut is about to be made and the auditionees are making their way to final line-up, you can see Paul's dance bag sitting in the middle of the stage.