Denis Leary, Molly Shannon Slay 'Nonsense Karaoke' on 'Fallon'

Comedians bring skeezy bombast and 'Superstar' power to warped versions of "Pour Some Sugar on Me" and "Waterfalls"

Denis Leary and Molly Shannon set new standards of quality for The Tonight Show's "Nonsense Karaoke" bit, singing Def Leppard's "Pour Some Sugar on Me" and TLC's "Waterfalls" with as much passion as the originals — even though their famed choruses now began, "Ask your sister for peas" and "Don't throw Jason's Barbie dolls."

Shannon kicked off the bit with "Waterfalls," dropping some slinking dance moves, adding a bratty sneer to a line about how it's "time to legalize the burgers of lunch" and — in place of TLC's pre-chorus "Listen to me…" — declaring the far more attention grabbing, "Snapple koozie!" Fittingly, Shannon ended her performance with some Superstar flair, twirling around and taking a quintessential Mary Katherine Gallagher bow.

Leary then trotted out in a flowing, lamé silver get-up and large, jaundiced sunglasses — the de rigueur look of Johnny Rock, the washed up rock star he plays in his upcoming FX series, Sex&Drugs&Rock&Roll. Unsurprisingly it proved to be the perfect wardrobe for warping one of hair metal's most lascivious anthems as well: "Play some boggle with Jeeves, and his hairless pug!" Leary sang with the expert sleaziness and bombast of a rocker who doesn't know the meaning of the term "has-been."

Jimmy Fallon had the unfortunate privilege of following both acts, but he still put his whole heart into Ed Sheeran's "Thinking Out Loud" while a montage of corny, romantic stock footage played behind him. Though Fallon tackled the song with impassioned vulnerability — difficult when singing about a cow that wants to look like Steven Urkel — Leary and Shannon arrived by his side and helped the host find the soulful wail he needed to bring home lines like, "Bo Jackson meows!" and "Bake me waffles in Snooki's barn!"

The trio closed out the song and "Nonsense Karaoke" together, singing softly and sweetly, "Baby, we found bugs in Pee Wee's car."