Derek is curled up on the sofa with a book when there's suddenly a rush of air and the scent of ozone. Barry and Castiel actually have similar entrances at times, but Barry smells like crackling electricity, and the air around him is warm once he's done speeding. Castiel smells a bit different and leaves the air momentarily cold.

He doesn't even react for a moment, and instead calmly licks his finger and turns the page. It's when Castiel pulls open the refrigerator that Derek finally lifts his head to look at him.

"For some reason I thought you'd at least land on my porch and knock," Derek says dryly, placing a bookmark into his book before standing up and stretching. "Don't touch any of Barry's lunchables."