Peter was Jess' rebound date following her breakup with Spencer. He was a douchey friend of Schmidt's and unliked by Nick and Coach, who ultimately stood her up at a nice restaurant and was never heard from again.
At Clyde's Bar one week after Jess moves into the loft with the guys, she's searching for a potential rebound to forget about Spencer with the help of Schmidt and Coach. They watch her hit on a guy like a 1940s pin-up, calling him "Sailor," when they're interrupted by Schmidt's party-loving friends, Benjamin and Peter.
They're both kind of douchey guys, so while Schmidt tries hard whenever they're around, and wants to be accepted by them, Coach could care less and refuses to return Peter's hanging high five. The men discuss the fact that Schmidt's not on the list for the Cowboys and Indians charity party, because their hook-up was always Nick's ex-girlfriend, Caroline.
Later, when Nick, behind the bar, is having a heart to heart with Jess, whose left boob is sitting in her chicken wings, Peter approaches to pick her up. He orders her another pink wine and tells her that he likes her glasses. "They help me see," Jess replies.
At the end of the night, Jess races over to her new roommates to tell excitedly them that she scored a rebound date - dinner, with food - with Peter, and they debate whether or not to tell her that her large white granny-panties are tucked over her skirt. As Jess dances away from them, smiling, they decide to let her have her moment.
The night of the Cowboys and Indians charity party, Jess is nervously getting ready for her date inside her bedroom. She recieves encouragement from her best friend, Cece, who also lets her borrow her little black dress for the date. When she walks into the loft living room, she gets approving nods from her roommates and pulls out her phone to text Peter. She's been texting him all day, she says, which makes Nick feel better about the fact he recently texted Caroline - a definite downgrade from how close they used to be.
When the guys get to the charity party, they step in line outside the club, arguing about their costumes, when they're approached by Benjamin and Peter. Right away, Nick asks what happened to Jess. "Dude, she texted me like, seven times. I just want to hook up!" Peter scoffs, laughing as he admits he's completely stood her up, without even a phone call.
As a result, Nick, Schmidt, and Coach don't go to the party, instead finding Jess at the restaurant to cheer her up with music from Dirty Dancing.