* AssPull - At the end of "Class Act" Coop suddenly knows real magic for no apparent reason when he has to subdue Kat.
** Millie, Lorne, Haley and Fiona suddenly getting all their memories of Kat being an alien erased at the end of the final episode.
* CanonSue: Fiona.
* CreatorsPet - Millie, '''Millie''', '''''[[RuleOfThree Millie!]]'''''
* DesignatedHero: Millie. Whenever she doesn't get what she wants, she screams at the top of her lungs until someone caves in, and she just generally acts like a SpoiledBrat, yet she is loved by ''everyone'', including Old Lady Munson (who hates pretty much everything) and Kat (an alien invader out to kill all humans), That alone almost qualifies her for MarySue status. In one episode, she finds out Coop was right about Kat all along, and she's... totally cool with it. And we're supposed to think this is sweet.
* {{Fanon}} - It's a common assumption that Cat Commander is Kat's father.
* HilariousInHindsight: In the Japanese dub, Creator/ChiwaSaito as Coop counts as this if you take into account she already played [[Anime/StrikeWitches roles]] [[VideoGame/BlazBlue involving voicing]] [[Anime/TsukuyomiMoonPhase cats or cat-like creatures]].
* JerkassWoobie: Coop. Despite his smugness at times and falsely thinking that Kat wants to take over the world, he does have to deal with Kat and Millie's antics, and being TheScapegoat for the town whenever something bad happens. Part of his attitude seems to stem from people shooting down his words every time.
* ParanoiaFuel - Not only your cat, but also your hamster could be an alien invader. As Mr. Cheeks says, '''"We're everywhere"!'''
* TheScrappy - Millie, and for good reason
* ToyShip - Coop + Phoebe, though its completley one sided
** Not so one-sided with Fiona.
* UglyCute - Kat.