i had a boss who used to like pranking.
i got really, really over it so i just didn't mention i had a doctors appt one morning.
he called at 10:00 asking where i was, told him i was f_king his missus.
he laughed, i didn't.
he then started to panic and started getting angry, told me to get into the office or i was fired.
said i needed to clean up first, then i'd be in.
came in at midday with a half-day's leave form for "medical reasons" with a doctors cert.
dropped the form, cert and a post it note with "punkd" on his desk and never got pranked again.....
dunno why...maybe he got tired of it.