A glorious reunion with three Smiths, two tin dogs, and genetically modified gargoyles who are allergic to their own oil.
The 10th Doctor and Rose are undercover in Deffry Vale High School after Mickey, aka Ricky, has (not booty-)called Rose to say that there’s something pretty alien going on. And he’s not wrong.
The Krillitane Brother Lassar, portrayed by Anthony Stewart Head (Giles in Buffy the Vampire Slayer), is himself undercover as the headmaster, Lucas Finch, along with the rest of his genetically modified gargoyle brethren who in turn make up the rest of the faculty.
When they’re not eating orphans (!), they’re using potato chips to turn the rest of the kids into computer chips. Clever, eh?