Ashlee Simpson is a proud mama, sharing pics of Bronx on Twitter.

Pete Wentz is a drunk moron, partying with skanks in Las Vegas.

With the useless but harmless "singer" home alone with their newborn son, her rock star husband was photographed getting wild in Sin City with a bunch of scantily clad dancers and a booze-fueled Slip 'n' Slide over the weekend.

Hey, beats diaper changing.

The Fall Out Boy bassist - sans wife of nearly one year - partied hard with about 50 band members, dancers and friends (including Girls Next Door star Holly Madison) following a sold-out show at the Palms Casino Resort on April 5.

"Everybody was going absolutely crazy," an eyewitness said. "People were even drunkenly playing makeshift Slip 'n' Slide with a mat and lubricant."

"And Pete Wentz was in great spirits. He was dancing and singing along to his band's own songs, while grinding up against the dancers. At one point he was even dancing on a pool table with the girls," the partygoer adds.

Earlier in the day, Ashlee Twittered: "I am beyond sad to leave my love ... My heart is breaking as we drive home." And also: "I need my hubs."

He just needs booze and lubricant, apparently.