Ellen brought out the big guns to kick off her first week of shows - after all, she's celebrating the 10th season of 'The Ellen DeGeneres Show.'
On Monday, P!nk joined Ellen for the season premiere, performing her hit song 'Blow Me (One Last Kiss),' and on Tuesday Ellen was joined by the one and only Britney Spears and her 'X Factor' co-star, Simon Cowell.
After Britney and Simon told Ellen how much they love K-Pop sensation Psy, Ellen surprised her guests and brought Psy out to join them. Psy gave Britney and Ellen a personal lesson in the 'Gangnam Style' horse dance choreography - which both ladies picked up immediately.
Check out the video:
Watch what happened when Ellen talked to Britney before the show: