DON'T do what I've done a couple of weeks ago - landed me my first HR meeting ever :D
I had to use my coworkers (lady around 50, not too clever with the computers) computer on remote desktop. As I was about to close it, I thought to myself "Perfect setup for a joke". On her computer, I went to https://pranx.com/hacker/ and put in on full screen. Literally like 30s later, our IT guy (he's in the same room as me) get a phone call and all I can hear is shouting in the earpiece. I say to him don't worry, I know what's this about, I'm going to sort it out. I went downstairs and boss's wife is running past shouting that we need to phone the police, I walk into the lady's room and she's hysteric. I say cool down, it's a joke.
Safe to say, they were not laughing (probably the fact that I still was, wasn't helping my case :D)