The first crossover of "The Fairly OddParents" and "The Adventures of Jimmy Neutron: Boy Genius" was considered noteworthy for combining two different animation styles, and exploiting both as much as you possibly could on a kids' cartoon. I'm not certain of how popular it truly was, but as I stated earlier, it was certainly noteworthy, and Nickelodeon clearly thought that a sequel was an automatic money-maker.The opening theme is almost identical to the first one, and as with many sequels and spin-offs, the jokes from the original are repeated. In fact, some of them are almost dangerously repetitive. Luckily, the plot isn't the same. In the first crossover, Timmy Turner needs a quick A for the science fair and tries to use Jimmy Neutron's lab to do so, and ends up falling in love with Cindy Vortex. In the second one, Jimmy and Timmy compete for Cindy, and Jimmy's much more open about his desire for her than usual. Having been recently defeated by Jimmy in his latest evil plot, Professor Calamitous(Tim Curry) finds out about the rivalry, and plots to use it to his advantage. Of course, just because somebody is an evil genius doesn't guarantee that somebody of average intelligence can't stall or defeat you, and in this case, it's Anti-Cosmo and the other escaped anti-fairies who stall the professor's fiendish plot.One positive aspect of the special is that more characters from both shows get to appear in the 2-D Dimmsdale and 3-D Retroville. Most of the characters from "Jimmy Neutron" appear as you'd expect them to. As a 2-D character, Sheen gets to perform more outrageous prat-falls and other sight gags that he never got to do on "Jimmy Neutron," although he probably could in both dimensions, as any other character can.There seems to be a notable pattern in TV-movie versions of both "The Fairly OddParents," "Jimmy Neutron" and the crossovers. With the exception of the criminally neglected "Win Lose and Kaboom," Jimmy's battles with his enemies seem somewhat standard adventure type tales. In "Fairly OddParents" movies, the battles are more Wagnerian, with slightly heartwarming(though not necessarily desirable) climaxes. But in Jimmy-Timmy combos, they're downright silly. And the silliness used in fighting Professor Calamitous in "When Nerds Collide," is way more than twice the level of the first Power Hour. It's kind of reminiscent of the Star Trek episode "Mudd's Women," but that doesn't take anything away from it.Somebody here wrote that this was better than the first Power Hour. Well, if you see this from the beginning, you may have some doubts about that, but not as you see the rest. Still a good one.