Use a mannequin head and place it next to your partner while they sleep. Wake them up and as they try to look at you they freak out as they see the fake head.

This prank needs some preperation but is really worth it. Your coworker will show up and his keyboard will be full of little grasplants!

Pick a 'needs to know it all' friend from your group, and send a text about a juicy secret.