Knocked Up

The story starts after Alison Scott, played by Katherine Heigl, and Ben Stone, played by Seth Rogen, have a one-night stand after meeting at a club. Several weeks later Alison learns she is pregnant, forcing two people with very different lives to decide whether they can raise a child together.

This Is 40, released in 2012, is a spin-off centered on Pete and Debbie, the married couple played by Paul Rudd and Leslie Mann in Knocked Up. Ben and Alison are not the focus of that later film, even though the two movies share Judd Apatow's comic world.

They play Pete and Debbie, whose strained marriage gives Alison and Ben a preview of what long-term commitment can look like. Their scenes also turn the movie into more than a pregnancy comedy, because the 2007 story contrasts new parenthood with an older couple already under pressure.

Both films were directed by Judd Apatow and use long conversational scenes, awkward sex jokes, and emotionally messy friendships. Knocked Up is more relationship-focused than The 40-Year-Old Virgin because the pregnancy plot forces Ben and Alison to deal with doctors, family expectations, and co-parenting.