The international superstar is chased by a group of girls, then takes the stage to perform hits from 'My World 2.0.'
RJ and Lily make progress towards regaining their friendship, and Lily gives the cheer squad a taste of their own pimple-causing medicine.
At 29 weeks, Lori gets her first ultrasound and discusses the option of moving in with ex-boyfriend Cory to raise their baby.
Mike brings a girl home to the smush room but Snooki and JWOWW don't think she's pretty enough for their housemate.
Josh gets his nose pierced, Erika is presented with a huge opportunity and Emily and Ty continue their cat and mouse game.
Emily grows frustrated by the tensions between her and Ty and a call from Josh's girlfriend interrupts his hookup.
RJ kicks off his "Uncool Like You" presidential campaign, in hopes of getting the "loser" vote.
Ashley sets Kristy up with popular girl, Erin, as her mentor, but Kristy doesn't feel like doing the things Erin tells her to do.
Lori struggles to decide what to do once her baby is born, while her parents promote adoption.
Linnea practices beatboxing with the other beatboxers at her high school, but when her coach tries to have her beatbox in public, she can't handle the pressure.
Audrina thinks Justin might want to settle down, and Heidi grows inpatient with Spencer when he shows no guilt over Heidi losing her job.
Jordan discusses the rivalry between Brian and sister Jessica, and the close relationship she shares with her twin.
Lizzie attends her baby shower, before finding out that Skylar was unfaithful and calls off their engagement.
Catelynn and Tyler get tattoos in honor of Carly and Farrah gets upset after being called "unmotherly" by sister, Ashley.
Nikkole struggles to find a homecoming dress that will fit her pregnant body and Josh comes to blows with one of Nikkole's friends.
After feeling unsafe around Joey's mother, Allie and Joey move in with his grandmother.
