While Marge takes Maggie to the hospital after Maggie swallowed an issue of Time magazine whole, Homer, Bart and Lisa go grocery shopping. Homer and many others mistreat the bag boys at the grocery store, and every bag boy in Springfield goes on strike. The bag boys form blockades around every store, causing a food shortage in Springfield as no one is able to enter the stores to buy anything, and the Simpsons begin to starve. Homer thus goes on a search for food when it runs out, and Santa's Little Helper finds a box of animal crackers in the attic, which is more than 30 years old.
Homer bites into a giraffe, but he does not know that it is made of solid gold, which indicates Homer has won a trip to Africa. The makers of the animal crackers initially refuse to honor the prize because the contest ended a number of years ago, and the makers are no longer even in food production, but when Homer is injured by the sharp corner of the box, they reconsider in order to avoid a lawsuit.
The family lands in Tanzania. When the family is in Africa, they experience such sights as the Masai Mara, Ngorongoro Crater, Olduvai Gorge, Mount Kilimanjaro, and meet with a group of Maasai tribesmen. During a vigorous tribal dance, Homer manages to enrage a hippo. It chases after the family, who escape on a raft going down a raging river. After surviving the plunge over Victoria Falls, and an encounter with a flesh eating plant, the family stumble upon a chimpanzee sanctuary maintained by the scientist Dr. Joan Bushwell (a parody of Jane Goodall). She claims to be researching the animals behavior when a group of poachers arrive to take the chimps.
The Simpsons try to hold the poachers but eventually they break into the sanctuary. The poachers are revealed to be Greenpeace activists, who prove that Dr. Bushwell is actually a chimp slave master, exploiting their labor at a nearby diamond mine. Worried that the Simpsons will report her to the authorities, Dr. Bushwell offers everyone diamonds as a bribe, which all except Lisa happily accept. The Simpsons leave Africa, and return to Springfield with the diamonds offered to them by Dr. Bushwell. On the plane, it is revealed that their former tour guide, Kitenge, is now president of the country, with the former president now the Simpsons' flight attendant.