Who can forget when Britney Spears and Christina Aguilera opened up the 2003 show with Madonna and Missy Elliott? And who can forget when Madge practically made out with Brit on stage? She kissed Xtina, too, but her kiss with the "Slave 4 U" singer made headlines. And so did Brit's ex Justin Timberlake when the cameras caught his reaction! "Oh I was very nervous and very shy," Brit said about the performance. "Like honestly, just being with Madonna, she has this presence about her. … I mean I'm a shy person in general, but I got very intimidated and I was like, not myself. I was not the confident Britney, you know?"