A coworker and I always joke back and forth at work. Very harmless, jovial kinds of jokes. Jokes I always feel can be repeated out of context and still be harmless. There's a whiteboard in the employee lounge, it's not used. I wrote my coworkers name and "Poopy Pants" beside it. They did not find that joke funny and reported me to HR. My boss talked to me and I have a meeting with HR later in the week. It's apparently serious enough my boss warned I could get fired. It was very difficult to keep a straight face over seeing pictures of the whiteboard and my boss angrily saying "Poppy Pants" every few sentences. I'm freaking out, but kind of want to see HR have to write the words "Poopy Pants" on my termination paper. I think the issue was that I wrote it and not just said it. So there's actual evidence of my "slander".
TL;DR: I wrote the words "Poopy Pants" on the employee whiteboard and may get fired.
UPDATE 1: After reading comments and talking to other employees, I think I've figured out the why of the situation. Other employees legit tease and make fun of him. I'm thinking he thought I was different, but when I wrote poopy pants, he felt I was just as mean as the others since I wrote it for others to see as opposed to just saying them to him privately.
UPDATE 2: For those saying I'm a mean ol' bully and should get fired and die alone in a gutter. Poopy Pants was the worst I have said to him. The worst he has said to me? A balding joke (I'm not sensitive about it, but it would understandable if I was upset). And a very close to racist skin tone comment about me and my family lineage (again, not a sensitive subject to me, but, if it had been a random person I would have taken it as a racial remark, but I knew his intentions were not hateful). I didn't mention these before, bause I don't agree with the "it's ok to hurt his feeling because he was mean to me" mentality and wouldn't justify what I did in HR's eyes (according to my boss anyways). That and he didn't write anything down, I did and he's shown himself to be a very well intentioned guy, up until this incident.
UPDATE 3: I haven't met with HR, but I had a long talk with my boss today. For him, anyways, he considers this matter over and done with. He feels like the verbal reprimand he, and later on this week HR will give, is sufficient. I'm pretty sure it's because I was fiercely apologetic and my boss said that he's certain if the coworker had come to me, I would have changed my behavior. Now, if I do something like this again, it's an automatic firing. So, once I meet with HR, I think I'll be ok. I'll also only be interacting with said coworker when it comes to work related matters only.
UPDATE 4: Talked with HR. Apparently there are different "levels" of misconduct. Insults, harassment, bullying and hate speech. After much investigating, their words, they couldn't find any way in which it was hate speech, unless he was incontinent and disclosed it to his employer, which he did not. Bullying and harassment have to be a pattern. Which this is the first documented incident. Which only left insults. Which only carry, at most, a written reprimand. So, as long as I keep my nose clean, I'm good.