Animal Motifs: Compassion says that she and Fitz are like the Doctor's pets. She compares herself to a cat, which thinks "My owner loves me and feeds me and takes care of me so I must be god." Fitz, she says, is a dog, thinking "My owner loves me and feeds me and takes care of me, so he must be god."
Liar's Paradox (parodied): The Doctor tries the Liar's Paradox on a security robot, which simply snaps, "Get off with you. You'll be asking me to calculate pi next," and keeps attacking him.
Strapped to an Operating Table: The Doctor. He's impressively calm about the whole thing, except for when he Screams Like a Little Girl just to be aggravating, especially considering the fact he's naked and facing a device that's supposed to bite out his heart.
