chunk: Graeme Willy (Simon Pegg) and Clive Gollings (Nick Frost) are British comic book enthusiasts and best friends who travel to the United States to attend the annual San Diego Comic-Con International, and to take a road trip through the American Southwest to visit sites significant to UFO lore. While driving on a remote desert highway at night, after a tense situation with some rednecks in a diner, Graeme and Clive observe a car driving erratically and then crash. They stop to investigate and offer assistance to the driver, who turns out to be an alien named Paul (voiced by Seth Rogen). Clive faints, but Graeme agrees to assist Paul and gives him a ride.
  Later, United States Secret Service Agent Zoil (Jason Bateman) arrives at the car crash site and informs his unseen female superior, "the Big Guy" (Sigourney Weaver), that he is closing in on Paul. She sends two inept rookies, Haggard (Bill Hader) and O'Reilly (Joe Lo Truglio), to assist Zoil.