Jimmy and friends find a strangely marked rock from outer space. While decoding the message on it, Hugh wants to bond with him, but Jimmy's to busy. After decoding the message -- a riddle, with implications of intergalactic prestige for any planet that answers it -- he and his friends (Libby, Cindy, Carl, Sheen, Goddard and Bolbi) sneak onto the military installation holding the rock to inscribe the answer. (The riddle was "In the dark, they appear without being fetched; in the light, they are lost without being stolen." The answer was the stars.) After being "beamed up" to their destination, they find themselves in an alien television studio, representing Earth in Intergalactic Showdown, a popular alien reality show hosted by a shifty host by the name of Meldar (voiced by Tim Allen), who can teleport anything in an instant. If they win the show, they get a new car. If they lose the show, they get their home planet (in this case Earth) destroyed. Three other teams are represented in this particular episode: the Brains, an evolved species with only brains and eyes for bodies; the Needleheads, high pitched, seemingly awkward, neurotic beings that indeed somewhat resemble nerve cells; and the Gorlocks, a warmongering, martial race (and the only humanoid team aside from the Humans).
Jimmy, overestimating his intellect and its usefulness in the games, causes the Human team to lose the first two events: "Florgus Ball", a strange hybrid of polo, jai-alai and (perhaps) Quidditch, with large mechanoid mantis-like beings named Florguses as transportation, and a test of speed and cunning, in which the team must retrieve a glowing mushroom from the mouth of a cave guarded by a deceptively cute, but powerful beast.
After the Survivor-inspired scene in which the team is forced to vote one of their members off the team (the vote is a 3-way tie between Jimmy, Cindy and Bolbi before Bolbi's misunderstood vote against himself casts him off), April (real name "Shee-AHHH!-toh"), the small but spry female Gorlock (voiced by Alyssa Milano), colludes with Jimmy, convincing him to work together to overthrow Meldar and the show itself.
In the next event, a Fear Factor-style eating contest, Jimmy (despite having calculated the exact strength necessary to spin the wheel and choose any generally human-palatable food) reluctantly allows Carl (who, given his appetite, could literally eat anything) to spin for the team. After a Needlehead fails to stomach a banana cream pie, Carl tries, and is enraptured with, an odd alien dish known as a "Plutonian Gut Chunk". After this event, Cindy sees Jimmy agreeing to ally with April and the Gorlocks, an alliance sealed with what Jimmy and Cindy interpret as a kiss, but is in fact a seal of trust to April's people. Both Cindy and April's teammate disapprove of this and stop the discussion.
In the meantime, the parents of Retroville have found themselves receiving the galactic cable network that supplies Intergalactic Showdown, and while Hugh Neutron has trouble staying away from the 8,999,999,999 (nine billion minus one) other channels his television set now carries (especially a soap opera called "Andromeda 90210"), the other parents convince him to keep watching the game show while they fix one of Jimmy's wormholes to travel to the set and save their children.
Eventually, Jimmy truly learns how to swallow his pride and work as a team to defeat the Brains in an obstacle course (including a false shortcut that leads to a mass hallucination on the part of the children that causes the parents to become zombies). The final event is based on "Who Wants to be a Millionaire." A human (Jimmy) and a Gorlock (April's dad) face off in a trivia showdown. They each have one lifeline, someone from their home planet who can answer the question. The Gorlock is the first to get his question, but he answers it wrongly, so it's Jimmy's turn. Meanwhile, the parents get the wormhole working, but just as they get ready to go through, Hugh comes out with a plate of nachos. He trips on a power cord, the nachos go sailing through the wormhole, Hugh dives in after them, and just as he goes through the wormhole shuts down. He ends up on the set of the show, right before Meldar gives Jimmy his question. When Jimmy tries to explain everything, Hugh says he knows everything because of space cable. Because of this, Jimmy realizes that Hugh probably knows more about alien culture than any of them, and has Hugh be his lifeline. The question was about "Andromeda 90210", Hugh's galactic specialty, but Hugh claims the question isn't answerable because it's worded incorrectly, so he gives the correct question and the answer, both of which are correct. They receive a special ceremony and their car. On the way home, Jimmy realizes that they need to save the other races' planets from being destroyed, so they go back and the children, Hugh, and the other three races combine their forces to fight Meldar and his robotic minions, take the gadgets that endowed him with the power to coerce his contestants into playing, and end the show forever, ensuring the safety of all planets involved from the wrath of Meldar.