Usually hearing the bleep of the door opening is enough to prepare him for someone's arrival, but this is a peculiar situation, and Peter, being the peculiar young man he is, manages to catch Bruce completely off guard. He doesn't even have the time to react to the sound of the door when suddenly there's someone right next to him, tapping him on his shoulder, making him actually startle in his seat.

"Jesus, Peter," he huffs, lips stretching into a smile as a hand settles briefly over his chest. "You're the one who needs a bell. A bit of warning next time, if you don't mind?"