A fire cadet (Sean William Scott) is out in the desert, practising his fire rescue skills for the local fire dept. test the next day, when a meteor crashes on top of his car and destroys it. The meteor ends up having alien organisms in it, that grow very quickly into various alien creatures. After which, Scott, who also works at the local gulf range club, is working one night at the gulf club party, when one of the gulf club member's woman, comes into the club hollering and screaming, that her boyfriend just got killed at one of the pond holes by some creature. Scott goes and finds alien creature that killed the gulf member and finds it dead, so he takes it to the local college and shows it to local college professors, David Duchovny and Orlando Jones, whom go back to the crash site, along with their students, and finds green moss and "slugs" growing already around the site. So, Duchovny and Jones take a sample back to the college with them. After which, the three then go to the local restuarant to eat, when a call goes out on one of the local police officers radios, that are eating there too, of a "dog" bite. So Scott recognizes the call code and all three go to check it out. They end up going to a local womans house that had two other house-wives there visiting, they hear a noise in the womans pantry and find an alien creature that looks like a dog, without a snout, she then tries to pet it and it ends up biting her, so she grabs a gun out of her drawer, but before she can do anything, it could not breath our air, and keels-over and dies. The three show up at the house and Scott ends up finding more creatures over the hillside lying dead. Jones ends up discovering that the creatures are migrating through the local mines, that run through the city. They then find one creature that gives birth to a creature that can fly and breath our air. They end up chasing the flying creature to the local mall, where Scott attracts it by hollering CaCa,Caca through the mall intercom. This attracts it to them, where they end up shooting and killing it. One of the young girls at the mall, that was shopping-lifting in the fitting room, was grabbed by the creature, she ends up getting dropped by it, when it falls, she then exclaims "I will not shop-lift again, I promise!" Then Duchovny exclaims "white or dark meat?" Jones answers, "you have to ask?" After which, Jones, Duchovny, and Scott, go to the crash site and find that the military are already there. They do get into the crash site, but basically get the brush-off by the officer in charge, played by Ted Levine(Monk). He tells them that he will keep them up to date. They also have a corky civilian scientist working for them, played by Julianne Moore. Duchovny finds himself attracted to her. So, they go back to the college, where Duchovny finds his office ramsacked and his computer files downloaded. So, Duchovny takes the government to court to get his materials back, which he doesn't win, so Duchovny and Jones sneek into the crash site to get more info. Duchovny goes in as a colonel and Jones as a private. Jones asks Duchovny why a colonel? He states that he was a colonel in the military and worked for Levine! Meanwhile, the general(Levine) is talking to the state governor, played by Dan Aykroyd, and tells him what would happen if they don't stop the aliens and wants to bomb them with napome. While Duchovny and Jones are in the site below, they end up being seen and getting caught. They try to tell the governor what is going on, but the Gen.(Levine)argues with them, until an alien creature that looks like a gorilla attacks the crew below, and ends up coming up to where everyones talking and attacks them. But, they end up shooting and killing it. Duchovny and Jones then get escorted out of the site, but Moore ends quiting the government and goes with Duchovny and Jones. They go back to the college, where Duchovny finds out, that heat makes the aliens grow faster! They try to warn the Gen. (Levine), but of course he ignores him. Then, two of Duchovny's students show up, one is Ethan Suplee/Stan Duber of the show "Earl" and find out that the Head-n-Shoulders shampoo kills the aliens! So Scott grabs a fire truck, they all load it with shampoo and they all go to the site, to kill the aliens. But, by then its too late and Levine bombs the site and the alien grows into a huge mushroom size blob. So they go ahead and drive the fire truck under the alien, to try to kill it with shampoo.