 There is a cut episode originally titled "Protect the Song of Love! Serena  plays Cupid" in which there are scenes where: Serena turns herself into an  adult to go into a bar, the outfit she is in looks a lot like that of a  prostitutes, and she also gets into the car of a man she just met. It  doesnt advance the main storyline too much, but the above reasons are  probably why it was never shown.