Justin Bieber, Megan Millally

JUSTIN BIEBER birthday exclusive! The music megastar is in the house for a spectacular celebration of his special day. You only turn 18 once, and for Justin, it's happening right here on the Ellen show! Ellen will be partying in style with the biggest teen pop sensation on the planet. She may even have a special birthday surprise! Plus, MEGAN MULLALLY was the hilarious high-pitched sidekick for 8 incredible seasons on the hit show, "Will & Grace." Now she's got a brand new show called "Breaking In," and she's here to tell Ellen all about it!