Action Survivor: Kylie. Over the course of the film, she manages to: grab one of the alien worms as it enters her mouth and pull it out again; burn said worm to death with a curling iron; escape a massive horde of worms by jumping off the roof of her house; take down a couple of worm-zombies (including a zombified deer) more or less by herself; and, ultimately, survive a flying couch to the facewith nothing worse than a broken arm. Not bad for a kid with fake nails and a penchant for taking long baths.
Berserk Button: The mayor isn't exactly a calm guy to begin with, but he really throws a tantrum after he discovers that no one has brought any Mr. Pibb, which is the only soft-drink he likes. This is after everyone's started turning into alien parasite-infected zombies, mind you.
Big Damn Heroes: Pardy shows up in a big blaze of glory, ready to save Starla, blow up the alien and kick some parasite ass. Subverted, since the alien knocks aside his grenade, it gets dropped in the pool and explodes there, and Pardy promptly gets his ass kicked.
Chekhov's Grenade: Subverted. They make a big deal of showing the viewer the SINGLE grenade that the Sheriff's department owns and the camera lingers on it for a moment. Later, when the hero attempts to use it, it's casually knocked aside and into a swimming pool, where it uselessly explodes.
Played straight with Kylie's nails which provide much needed grip during the initial attack.
Cluster F-Bomb: The whole film, but especially anything the Mayor says.
Crazy Jealous Guy: Grant does not like the idea of other guys getting close to Starla. It's bad enough before he gets possessed by an alien death-worm.
Decoy Protagonist: Bill's something like this; the audience is set up to expect him to become the ass-kicking Action Hero when the moment calls, but when the action really kicks off while he's not that incompetent and certainly isn't cowardly, it is pretty clear that he's completely out of his depth, and pretty much every moment that's set up to make him look like a Badass ends with him either running away or getting his ass kicked. He also needs to be rescued more than once by Starla and Kylie.
Nathan Fillion certainly confirmed that one of the things he really enjoyed about playing Bill was his bewildered and terrified "what the fuck is going on?!" reaction to almost everything that happened, rather than reacting like a standard Action Hero would.
Deep South: The film is set in Wheelsy, a small town in South Carolina.
Diagonal Cut: When a single guy tries to stop Grant, the latter casually whips a tentacle at him. He looks, confused, for a few seconds, while blood starts pouring out of a perfectly vertical cut from his head to his groin, before he splits apart.
Homage: Most obviously to Night of the Creeps. Starla teaches at Earl Bassett Community School, the mayor's name is R.J. MacReady, there's a store in town called Max Renn's, and Bill mentions the Raglan and Castevet farms. The scene of Kylie getting attacked by a slug in the bathtub has definite echoes of Shivers, as well.
Mercy Kill: Bill delivers this to Mayor MacReady after the discovering that the latter has begun to get all "womby."
Morality Pet: Starla could probably qualify as this for Grant before he got infected. Definitely qualifies for him (and the Hive Mind as a whole) afterward in that she's the only human he/it/they cares enough about to not infect.
The Power of Love: Subverted, but not how you think. After being infected, Grant tries and succeeds at resisting the urge to eat Starla, and has his drones bring her back home and dress her in silk and comb her hair lovingly. At the end she even manages to prey on his love for her to get in close and stab him. Pity it wasn't in a vital area... which, considering he/it was a mass of alien blubber, tentacles and human bodies, he may not have had one other than his brain.
Word of God is that the real Grant was killed as soon as the parasite entered his body. The creature, however, retained Grant's personality and memories and was thus influenced by it (notably, Grant's love for Starla).
Rant Inducing Slight: Macready has been through a pretty awful night, and he's been reasonably stoic about it (i.e., he's been no more of a profane loudmouth than usual), but the lack of Mr. Pibb in the cooler was just the last straw.