Well, that's one way to advertise! There's been a whole lot of buzz about the Full House actors reuniting for a Super Bowl yogurt commercial, and during the group's Wednesday appearance on Good Morning America, John Stamos created a stir of his own when he decided to show off his underwear. Have mercy! Looking into the camera, he unzipped his pants to reveal Calvin Klein underwear adorned with pictures of the Dannon yogurt featured in the group's Super Bowl ad. When he wasn't stripping down, John linked up with Rihanna, who was also a guest on the show, and she managed to do one seriously epic photobomb. Take a look at his week with the rest of the Full House guys plus the trio's hilarious backstage antics on GMA.