Did anyone else notice...
In the scene with Mia's 21st birthday ball she has to dance with numerous partners with all different styles (one may say) of dancing is a direct reference to Meet Me in St. Louis during the winter ball scene where Judy Garlands character Esther has to dance with many different partners (all with their own technique) and is finaly saved by the one she loves, just like in Princess Diaries 2.
"Love lifts us up where we belong, where eagles cry on the mountain high"