When Alison Scott is promoted in E! Television, she goes to a night-club to celebrate with her older married sister Debbie. Alison meets the pothead reckless Ben Stone and while having a small talk with Ben, Debbie's husband Pete calls her to tell that their daughter has chicken pox. Debbie leaves the place but Allison stays with Ben, drinking and dancing along all night; completely wasted, they end up having a one night stand. Ben does not use condom and eight weeks later, Allison discovers that she is pregnant. She calls Ben and they decide to try to stay together and have the baby. However, Ben needs to grow-up first to raise a family of his own.
Seth Rogen, Paul Rudd, Leslie Mann, Katherine Heigl, Jason Segel, Jay Baruchel, Jonah Hill, Martin Starr, Nick Thune, Tim Bagley, Ken Jeong, J.P. Manoux, Ana Mercedes, Adam Scott, Charlyne Yi, Iris Apatow, Maude Apatow, Joanna Kerns, Harold Ramis, Alan Tudyk, Kristen Wiig, Bill Hader, Craig Robinson, Loudon Wainwright III, Stephanie Mnookin, Mo Collins, B.J. Novak, Tami Sagher, Brianna Brown, Catherine Reitman, Paul Feig, Ben Meyerson, Wayne Federman, Matthew McKane, Steven Brill, Nadine Griffith