This was around 2000 when IRC (internet relay chat) was going strong. For the young ones, this was pure text based chatting, both person-to-person and public rooms, without any of the fanciness. Facebook and Whatsapp didn't exist back then. Some hardcore geeks still use it to this day. I have to mention this recent xkcd here: http://xkcd.com/1782/

On Windows, by far the best IRC program was mIRC. Oh the nostalgia! It was pretty nice BITD and it supported plugins which made it pretty awesome (you can't do that with Whatsapp, can you?). I wanted to play a joke on a guy who I was pissed at for some reason. So I wrote a mIRC plugin that randomly made typos in the text he typed.

Imagine what you would type if you had to type 2x as fast as you normally can, with your non-dominant hand, while drunk. It added and removed some random letters here and there, and replaced some keys with adjacent keys. The best part was that you would see the original text in your mIRC, but mIRC would send the garbled text to the IRC network.

so a tpicla senntenc wluld lok lie thid. Yiu cold kinfa znderhstannd what tjey mant, buzt t was rettty bad.

I didn't have any hacking skills to deploy it, so I just used some social engineering skills to install it on his computer without them knowing. And then hilarity ensued. I don't remember how long it lasted or how it stopped but it quickly made me forget why I was pissed at him. And then some. People were like wtf, is he high or what, he used to type normally and then this happened. And when they asked him, they were clueless because to him, everything looked normal. So that just added insult to injury. And I don't even feel bad because it was so funny, even now I'm laughing. I don't know if he ever realized this, probably just reinstalled mIRC after some point, but I'm sure he would understand the joke.