My coworker finally caught on that I’ve been slightly pranking him for a while.
We work in a six story building after hours. I work part-time so I leave about two hours before my other coworkers. When I leave, I like to send an empty elevator up to his floor, knowing that he likes to take his break in the lobby (even when it’s not his break, you know as you do). I never get to see his reaction, but I like to picture him jolting upward when the elevator door starts to open.
I think he finally caught on cause now every once in a while an empty elevator shows up on my floor. Neither of us have acknowledged the elevators, but I know he knows and he knows I know. All in good fun.