It's revealed that Mac's full name is Ronald McDonald.
The bartenders at the reunion, as well as the man standing at the bar, are the Followill brothers: Caleb, Nathan, and Jared. They are in the rock band Kings of Leon.
The music playing when Dennis is talking to Frank and Maureen is the same beat as in Mac Bangs Dennis' Mom (2006) when Frank was singing "go for it" at the club.
The idea that Tim Murphy slept with Dennis' prom date was first brought up in Underage Drinking: A National Concern (2005) when Charlie and Mac try to get back at Dennis for boasting about his popularity in high school.
Rob McElhenney's high school alma mater, St. Joseph's Preparatory School ("The Prep," 18th and Girard Avenue, Philadelphia, PA), is the setting for the gang's high school reunion, though in actuality the Prep is an all-boys school with a coat-and-tie dress code. There are also several references to the school in the first season, especially the pilot, along with areas of Philadelphia (e.g., Lemon Hill in Fairmount Park) popular among Prep students.