We had a Christmas Party in our office in December and the office looked fairly trashed in the morning.
I took a photo of a colleagues desk and photoshopped burn marks on it, sending it to our group WhatsApp saying the bosses are furious and whatever they did after I left has left the guys in so much trouble.

It was a horrendous photoshop too, because I had nothing but PowerPoint to use - but everyone still believed it.

Most of the guys had booked that day off to deal with hangovers so it wasn't till the Monday that they realised it wasn't real!