This prank is best reserved for someone you really do not like since the clean-up can be messy.
Take a container of talcum powder, flour, or even lots and lots of dust. You will also need a leaf blower or even a powerful vacuum like a shop vac.
Take a thin tagboard sheet like a box of Cheerios and use the tagboard to help place the powder as far under the door as you can. Unless of course you have a shop vac, then load the powder into the shop vac.
Fold the tagboard in half with a sharp crease and tape one end closed and one end to the nozzle. Stick the open end under the door and fire up the device! Work that nozzle back and forth and make sure you work that pile you shoved under the door and blow it all away.
Use the device to clean up as much evidence as you can outside the door so there is no sign what prank has been pulled.
The powder will cover everything. It's quite a mess and difficult to clean.
By the way, before you go through this whole set-up, check first to make sure the door is not in fact unlocked.