Lucifer! Lucifer! Lucifer!

While interrogating Sharon Osbourne, Decker asks her if she bit a head off a bat, to which Sharon responds that it actually was her husband who did that. This is a reference to a real event, during which Sharon's husband Ozzy Osbourne bit a head off a bat during a live show. This event took place in Des Moines, Iowa, U.S. on January 20, 1982. The bat was thrown on stage by a fan, and Osbourne claims that it was only after biting it that he realized it was, in fact, a real bat and not a toy. After the show he went to a local hospital to get rabies shots.

SPOILER: At the penthouse, Chloe is startled when Michael comes up behind her. However, his footsteps echo loudly on the floor, and the noise would have warned her he was there.

Chloe does hear Michael coming. However, as she is about to do something considerably risky (and after having direct experience with upset celestials at full power), her slight jump reads as from nerves rather than surprise.

References 2001: A Space Odyssey (1968)