The old lady from "Movie Massacre" asking "Is this Earth?" At first, both Lucy and the audience assume she's just senile...but then it turns out that she was an alien queen in disguise...she was asking about the Earth to help her invasion!
Also from "Movie Massacre", after Ben pulls the pins from the grenades, they take a good 5 seconds to blow up. This can be explained with them being "prop grenades" and possibly tampered with by Ben and the alien spaceship's tractor beam interfering with the grenade fuses.
With the exception of "Orcs & Dorks" where Kate used her powers to make things more fun, she actually never uses her powers unless it's to save her friends or when her brother Ben asks her to, which would make Ben a sort of Morality Pet to Kate, but this implies something else: he can make her use Black Magic just for the sake of making a movie, and Ben may not even grasp the full consequences. Given that the most we've seen of Kate's powers is turning people into creatures or creating monsters out of thin air and bringing the dead back to life, let's just hope she isn't powerful enough to literally bring Hell on Earth and that her brother never gets the idea of making a Cosmic Horror Story, because the only thing standing between a somewhat stable world and complete chaos is a lunatic filmmaker's wild imagination and the limits of her sister's powers.
We do see her summoning an army of demons in one scene of Out of Time, causing The End of the World as We Know It. That begs the question, what caused such an event?
In "Out Of Time", Lucy, who's hanging onto one of Big Ben's clock hands thanks to Ben and Kate's antics, writes "STOP THEM LUCY" with her Permanent Marker (that lasts for 168 years) to warn her "future past" self to stop Ben and Kate from messing with timelines. She's lucky her marker lasted that long and that nobody seemed to have noticed her writing or erased it during all that time, or our protagonists would have been stuck in a Stable Time Loop where they end up dying.
Also in "Out Of Time", Father Time then teleports everyone Ben and Kate brought throughout their time travel shenanigans back to their respective timelines, but when he entered through a portal, said portal accidentally killed a cockney kid who was unlucky enough to be in its way when it spawned, so who's to say the people he sent back in time didn't accidentally appear at the wrong place, or even in the wrong timeline?
