The movie picks up five years after we last saw Pete and Debbie, the married, affluent couple whose domestic squabbles and idiosyncrasies proved so entertaining in Knocked Up. 

Paul Rudd and Leslie Mann are back, naturally, along with Mann and Apatow's real-life daughters Iris Apatow and Maude Apatow as Charlotte and Sadie.  Jason Segel is also reprising his supporting role from that film (or he's playing a wholly different character, like Jonah Hill in the shared universe of Forgetting Sarah Marshall and Get Him to the Greek), but neither Seth Rogen nor Katherine Heigl will be appearing, it seems.

The trailer is available in high definition at Yahoo! Movies, where it just premiered.

As usual, the director of The 40 Year Old Virgin, Knocked Up, and Funny People – also executive producer of dearly departed television series Freaks and Geeks and Undeclared – has put together a pretty amazing cast of comedic personalities.  That cast is led by Mann and Rudd, obviously, but also includes Melissa McCarthy, Chris O'Dowd, John Lithgow, Albert Brooks, Lena Dunham, Robert Smigel, Megan Fox, and Charlene Yi, another Knocked Up actor who may or may not be playing the same character (probably not).

This Is 40 arrives in theaters on December 21st, and will be the first of Apatow's films to be released outside of summer.