"Legally Blonde" star Reese Witherspoon, 25, will host Sept. 29's season premiere of NBC's "Saturday Night Live." New York's Daily News also says that the evening's musical guest will be Alicia Keys, 19, whose current hit is her first CD, "Songs in A Minor." "SNL" will be entering its 27th season and is perceived to be experiencing something of a comeback after some earlier slack seasons. Having the Bush-Gore presidential election as fodder for its satire is being cited as one reason for the show's resurrection. Ratings-wise, the program averaged 8.6 million viewers last year. As for Witherspoon, she recently told PEOPLE that being a ditz "has nothing to do with hair color and everything to do with needing a nap." She was referring to the fact that in her hit summer comedy she played a flighty Harvard Law School-bound airhead. In real life, however, the actress stays pretty well-grounded. "It's good to go to a premiere and then come home and change diapers," said Witherspoon, who gets plenty of home schooling from her husband, actor Ryan Phillippe, 26, and their year-old daughter Ava. "I was a neophyte as far as babies are concerned. Ryan's mom ran a daycare center when he was a kid, so he can diaper in nine seconds flat."