The muscles of his stomach jump slightly, and tighten - a tiny shiver at the touch of Aziraphael's mouth.

"Tickles," Crowley informs him breathlessly - though whether this too means Aziraphael's mouth, or instead the soft stroke of his hand, is apparently a mystery. Crowley threads his hand back through Aziraphael's hair, thumb circling the spot just behind the angel's ear.