Boomer

Boomer was revealed to be Matt's friend from the party Julie went to.

Season 4
Boomer hangs out with some other friends of Matt at his friend's birthday party. When Susan follows Matt to his room, Boomer claims that he wasn't the one to invite a "stripper", and then yells at Susan, telling her to "take it off". After he finds out that Susan's pregnant, he shows himself disgusted.