Bruno Mars Hosts 'SNL,' Debuts 'Young Girls': Watch

"Saturday Night Live" scored this week with a nerded-outBruno Mars singing Green Day and unannounced guest star Tom Hanks stopping by to mock the presidential debates.

Host and musical guest Mars continued the proud tradition of Justin Timberlake and Mick Jagger by pulling "SNL" double duty, though he admitted during his monologue he had no acting or comedy experience.

"I've never even done a shampoo commercial, which is crazy" (given his fabulous head of hair) he said. He asked the audience to be forgiving, and broke into a song that started off self-effacing, but grew into a confidant riff on how he was going to be an amazing host.

"But please be gentle," he sang at the end, "because it's my first time."

Mars continued his hot streak in a sketch which took us inside the offices of the music streaming service Pandora and forced him to sing in the style of Green Day's Billie Joe Armstrong.

Yes, the results were hilarious.

Pandora runs into an emergency, with the vocal tracks for Green Day songs somehow being taken out of commission for a while. It's up to the nerdy intern (Mars) to sing the tracks live so listeners calling up the Green Day channel will be able to enjoy the songs. He (sort of) gets Green Day right, and then must move on to Aerosmith, Justin Bieber and Katy Perry.

Bruno Mars also performed "Locked Out of Heaven," the first single off his upcoming "Unorthodox Jukebox" album, and debuted a new track, "Young Girls."

Hanks made an appearance near the end of the episode's cold open, meanwhile, which tackled the second presidential debate between President Barack Obama and GOP challenger Mitt Romney.

And in a recurrent series of ads, "SNL" also mocked Brad Pitt's much-maligned Chanel commercials that hit recently, with the actor promoting everything from Taco Bell to dog condoms.

The next episode of "SNL" airs Nov. 3 with host Louis C.K. and musical guest Fun. performing.