In the town of Mossingham a man named John and his
Border Collie Bingo discover the landing of a
UFO. On nearby Mossy Bottom Farm,
Shaun and the flock attempt to pass time with several dangerous activities, only for sheepdog
Bitzer to stop them. After being banned from having a barbecue for dinner, Shaun decides to order pizza, but discovers that the boxes are completely empty upon their arrival. The next morning, Shaun discovers a trail of pizza crusts and encounters the visitor. The visitor introduces herself as Lu-La, a tentacled dog-like alien from the planet To-Pa who can mimic sounds and levitate objects. When Shaun introduces her to the flock, she causes mischief with a
combine harvester, damaging it while transforming a field behind the farm house into unintentional
crop circles. Taking advantage of the recent news of alien sightings, the
Farmer decides to create an alien-based theme park, "Farmageddon", in which he can earn money to afford a new harvester. The Ministry of Alien Detection's (M.A.D.) leader, Agent Red, who has been obsessed with proving the existence of aliens since seeing two of them as a child, investigates the UFO claims. Meanwhile, Lu-La and Shaun track down the UFO, followed by Bitzer, who spots them while posting flyers for "Farmageddon" in an alien costume. On board the UFO, Lu-La transmits her memories to Shaun, revealing that she is actually a child and accidentally launched her parents' UFO while playing on it. They realise they need an egg-shaped device that was dropped by Lu-La when leaving the UFO, to activate it. M.A.D. mistakes Bitzer for an alien and follows him to the UFO, capturing it with Shaun, Lu-La, and Bitzer still on board. They also find the device and take both it and the UFO back to their secret base. At the base, Shaun and Lu-La slip out and manage to retrieve the device, successfully restarting the ship and escaping the base. They set a course for To-Pa; en route, Shaun ignores Bitzer's instructions not to press the ship's buttons and causes it to crash-land back at the farm. With the UFO destroyed, Lu-La is left heartbroken. Feeling guilty, Shaun discovers that the device can be used to send a
distress signal if he reaches a high enough point. Shaun suggests that he and Lu-La attempt to reach the top of the Farmer's "Farmageddon" theme park tower to make contact. With the help of the flock and Bitzer, Shaun and Lu-La climb the tower while the Farmer launches a show at the theme park. Meanwhile, Red arrives and chases Shaun and Lu-La up the tower with a mecha. Shaun manages to knock Red off the tower and successfully sends a distress signal to To-Pa. Lu-La's parents, Ub-Do and Me-Ma, quickly arrive and reunite with their daughter. Red eventually welcomes the aliens, recognizing them as the aliens she saw as a child. Shaun, Bitzer and the flock bid the aliens farewell, while the "Farmageddon" theme park and show receive rave reviews as the entire incident is regarded as part of the show's
special effects. On their way back to To-Pa, the aliens discover the Farmer has accidentally boarded their UFO, prompting them to take him back to Earth. The next day, Shaun, Bitzer, and the flock play with a
frisbee while the Farmer tries out his new harvester; the frisbee gets caught in the harvester's machinery and causes it to explode. ==Voice cast==