When a meteor lands in Retroville, Jimmy Neutron finds out it's "message meteor," something Neutron is familiar with, and thus wants to translate. In fact, due to his scientific wizardry, Neutron has had more contact and more experience with aliens, but nobody is willing to listen to him, something our boy genius faces throughout much of the movie. Once he finally gets the chance to do so, he Cindy Vortex, Carl Wheezer, Sheen Esteban, and the rest of his friends are sucked into deep space onto another freaky alien world that claims to be superior to ours(Don't they all in these movies?). Upon arrival in this alien world, they meet an evil game show host named Meldar(Tim Allen) who slanders all earthlings as "jellybags," and tells Jimmy that they've been sending meteors with messages imprinted on them for 500 years and nobody from earth has bothered to read them until today. Somebody should've told Meldar that earth didn't have television until less than 100 years ago. The idea of "Intergalactic Showdown" is for numerous creatures from each planet to prove they're the dominant life forms. The winner gets a fantastic prize package(apparently), and the losers have their home planets blown to bits. Forefit, and your home planet is destroyed anyway, so Jimmy and his friends realize they have no choice but to play. Clearly, it's a good thing nobody was teleported to this game show until now, because nobody from earth would be able to grasp the concept of "reality" game shows, let alone normal ones. It also makes you wonder how many other worlds were destroyed prior to the arrival of Neutron, his team and his competitors.
After losing big to their alien opponents, one of them, specifically a Gorlock teenage girl named April(Alyssa Milano) offers a truce with Jimmy so she can plot to destroy the game show. This increases the tension between Jimmy & Cindy Vortex, and if you've seen enough episodes of the regular series, you'd realize that Cindy harbors a crush on Jimmy, but it's far more subtle than Helga Pataki's crush on Arnold, of which she agonizes relentlessly behind his back while tormenting him. But crush or no crush, Jimmy knows he has to win, because it's not just about team victory or even personal victory. It's about defeating evil. Jimmy is a scientist, and by nature a humanist. Therefore he knows that win or lose, the show must not go on.
Shamefully, while this is one of the better extended versions of the series, it's not available on DVD or VHS, unlike "Jet Fusion" and "Attack of the Twonkies." You'd think that Nickelodeon and it's parent company Viacom would have enough marketing sense to do so, but then again they don't have enough sense to put the complete "Daria" series on DVD either. So as of this writing, your only recourse is to wait until "Win, Lose and Kaboom" is rerun on Nick and tape it yourself.