In an attempt to end a pledge drive which interrupts a favorite show of his on PBS (a Thames Television British sitcom entitled Do Shut Up), Homer pledges $10,000 to the network. Homer is applauded for saving the network, but it quickly becomes apparent that he does not have the money, prompting pledge drive host Betty White and a mob of characters and personalities from various PBS shows (including Fred Rogers, Yo-Yo Ma, the Teletubbies, Big Bird, Oscar the Grouch and Elmo) to chase him through the streets. Fortunately, Reverend Lovejoy saves Homer after he runs into the church. Reverend Lovejoy gets Homer past the mob by hiding him in a bag disguised as a sack of children's letters to God. Lovejoy puts Homer on a cargo plane to the South Pacific, where he will become a missionary in Micronesia despite Homer's lack of religious faith (to the point he mistakenly calls Jesus "Jebus").
Homer calls back to Marge in Springfield with a radio, during which he promotes Bart to "the man of the house", Lisa to "boy", Maggie to the "brainy girl" and the toaster to "Maggie", making Marge a consultant. Bart replaces Homer at the Springfield Nuclear Power Plant, where Mr. Burns criticizes Homer's record and, not recognizing whom he is talking to, pokes Bart with a stick. After coming home from a hard day at work, Bart agrees to take Marge out for dinner one night.
Homer arrives on the island and he meets Qtoktok and Ak. He also meets a native girl who acts and sounds exactly like Lisa that he names "Lisa Jr." At first, he is so desperate that he drops to the ground writhing and crying "Oh God!" repeatedly (which the natives all imitate, following his example). The natives are first portrayed as noble savages, ignorant of and unspoiled by North American civilization. Homer eventually begins trying to teach them about religion, but realizing that he knows nothing about it, he tries something new and decides to build a casino on the island, which he names "The Lucky Savage". This introduces alcohol, gambling, and violence to the island, and ruins the natives' virtuous way of life.
After the failure of the casino, Homer builds a chapel in penance, but he and Lisa Jr. ring the bell too loudly, causing an earthquake that releases a river of lava. The chapel, carrying Homer and Lisa Jr., starts to sink into the lava. As the two are about to meet their deaths, the scene cuts to another pledge drive, this time for the Fox network. It is revealed that Homer's adventures and mishaps were all recorded while he was on the island, but the show is in danger of cancellation, as is the entire network. Various Fox show personalities are manning the phones (including Thurgood Stubbs from The PJs, agents Mulder and Scully from The X Files, Hank Hill from King of the Hill and Bender from Futurama), joined by a cranky Rupert Murdoch and hosted again by Betty White, who entreats the viewers to help keep "crude, low-brow programming", such as Family Guy, on air. Bart calls in and pledges a $10,000 donation. Murdoch remarks that Bart Simpson has saved his network, to which Bart replies "Wouldn't be the first time".