Cheers to proving 'em wrong. When NBC chose a tall, lanky unknown comedy writer with the impossible name of Conan O'Brien to succeed David Letterman as host of Late Night in 1993, few people outside (and truth be told, inside) the network thought the redheaded underdog would last five months, let alone five years. During his first two years on the air, O'Brien was signed to a succession of short-term contracts, giving NBC an easy out if the show tanked. But the comic(right, with cohost Andy Richter, in a vintage photo marking their debut) proved his naysayers wrong, steadily building both the quality of his quirky show and its popularity. On September 15, he'll host a fifth-anniversary special, getting a well-deserved bow in the prime-time spotlight.