I used to like r/AssHatHackers as a teenager:
> You've heard of Black Hat and White Hat, now there's Ass Hat Hacking.
> One day in Comp Sci class I created an infinite loop program that ran on my friend's computer while he was in the bathroom. He promptly called me an Ass Hat. Thus Ass Hat Hackers was born.
> For hacking to have fun and mess with people.
My buddy once pranked my other buddy with an infinite loop batch file that opened Chrome a thousand times and crashed the computer. I tried to do the same thing with calculator, but found that it wouldn't loop until the calculator window was closed. Thus the Calc.EXE Hydra was born. Every time you closed one, two would take its place ;)
Beyond that, I loved talking to my friends while plugging in my mouse to their computer. I found if you maintained eye contact, they wouldn't notice even if you were being really obvious. Then you just wait and jiggle the mouse every few minutes.
Lastly, I would put people's Chrome into "compatibility mode", which meant that whenever they opened the browser, the entire screen would posterize to 256 colours and it would look crazy. One time my classmate opened his browser and freaked out, and the school was going to call IT. I said "I'll fix it, looks like some idiot changed it to compatibility mode" while shaking my head. It was me who'd done it a week earlier.
