I convinced some of my co-workers that we have a ghost in the building.
Why would you tell them that there's a ghost in the building?
I wanted to play a prank on them and tell them there's a ghost.
It isn't nice to lie to people. Especially to people you work with every day. This could really scare some of them.
It's just a fun little prank to play, no one is scared.
The subject of ghosts could be very worry some for people. You may think it's funny, but your co-workers may be scared. Try to find a fun game that all of your co-workers can play and enjoy.