Donny Osmond gets a warm reception when he returns to Las Vegas, following his "Dancing with the Stars" win -- and ET is there.

Donny -- with his disco-ball trophy in hand -- is greeted by the cast and crew of his Flamingo show, including comic George Wallace, who says, "I am so proud of you. I told you guys he was going to take it all the way to the top!"

Then, when the two are actually on stage, sister Marie teases him about how he moaned and groaned nightly because he was so sore!

And Donny responds, "You know why I did this? To keep up with her career. I had to beat Marie. She came in third and I came in first. I am now officially a better dancer than Marie!"