Asked by an interviewer with The Advocate whether Knocked Up would usher him into the Frat Pack, Rudd said he was a 'pledge' that hasn't 'been initiated yet into the brotherhood'. A year later, Paul Rudd was called a Frat Pack member by the New York Post and other publications. In 2005, Details Magazine called Judd Apatow, Adam McKay, and Todd Phillips 'The Frat Packagers'. While hosting Saturday Night Live in September 2005, Carell indirectly claimed membership by mentioning Stiller, Vaughn, Ferrell, Owen Wilson, and Black, and saying he was 'one of those guys now'. The previous year, USA Today had listed Carell, Paul Rudd, David Koechner, and Leslie Mann as the Frat Pack's 'Junior Varsity'. Reilly, David Koechner, and Steve Carell were also included in the Pack. Initially, the core members included Jack Black, Will Ferrell, Ben Stiller, Vince Vaughn, and brothers Owen Wilson and Luke Wilson, all of whom were recognized by USA Today in an early feature. Ben Stiller has decried the use of the term, saying, 'I think the whole thing about the Frat Pack group is completely fabricated anyway.' Membership Owen Wilson (left) and Ben Stiller (right) with Amy Adams in May 2009 promoting Night at the Museum: Battle of the Smithsonian

The name is an allusion to the Rat Pack (and the later Brat Pack), combined with a reference to the group's popular fraternity-related film Old School, and the sophomoric style of humor employed in many of their films. By 2005, Entertainment Weekly had dropped the 'Slacker Pack' term and followed suit, referring to the aforementioned crop of actors as the 'Frat Pack'. Before USA Today dubbed this group the 'Frat Pack', Entertainment Weekly had referred to them as the 'Slacker Pack', having earlier coined the term 'Frat Pack' to describe actors Leonardo DiCaprio, Tobey Maguire, Matt Damon, Ben Affleck, and Edward Norton, who have acted together in dramas. The term was used by USA Today in a June 2004 story and was soon picked up by other media outlets. The group is usually considered to include Ben Stiller, Owen Wilson, Luke Wilson, Will Ferrell, Steve Carell, Jack Black, and Vince Vaughn. The Frat Pack is a nickname given to a group of American comedy actors who have appeared together in many of the highest-grossing comedy films since the mid-1990s. Not to be confused with Rat Pack or Brat Pack.

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