Johnny Carson was the undisputed king of late night for decades. As he presided over The Tonight Show, he invited thousands of stars into his studio to talk, laugh, perform and charm his audience. When he died on January 23, 2005, he left behind shoes that were hard to fill. In honor of his legacy, we're taking a moment to look back at some of his most memorable guests, from Groucho Marx to Joan Rivers to Robin Williams. Look through the photo gallery and click any photo for more info. Then scroll down to see Johnny's hilarious 1991 Tonight Show interview with the great Robin Williams, as well as more memorable Tonight Show moments.