Christina Aguilera Shows Off Major Weight Loss, Justin Bieber Attends Selena Gomez’s Birthday Party: Top 5 Stories

Selena Gomez; Christina Aguilera; Kourtney Kardashian
Selena Gomez; Christina Aguilera; Kourtney Kardashian Kevin Mazur & Gregg DeGuire/WireImage; Brian Prahl / Splash News