You cannot nickname yourself.
I did not name myself Jefferson, that came from working at Safeco.
Kids often call me Mr. L for short. I have some that call me Senor Jefe because I joked with a class one day about Jefe vs Jeff and the meaning.
I also am known by one group of kids as Mr. Banana, Sir.
Mr. Banana, Sir.
It was PI Day a few years back and some kids were nicknaming everyone types of pies based on the colors that they were wearing. I was wearing a yellow race tee. I refused to be call "Banana". I was mostly playing along, but that was not something that I wanted to stick. I replied that i wanted to be "a golden delicious apple". They were having none of it.
So, all day it went on.
"Can we call you MISTER Banana?"
On it went.
I figured it would fade over the day, but at least three of these kids were really persistent.
Late in the day I joked, "That would be Mister Banana, Sir, to you."
They were excited.
Oh, well. It was only for the last period of the day or so.
It went on for weeks. One student wrote a joking epic poem about Mr. Banana, Sir, that I still have somewhere and should post when I actually find it.
I finally had a chat with an administrator, and we decided that since it was meant in fun and that I was a sub with a sense of humor that I should just go with it as it was clear that I was being accepted and "getting over" with them as a group. I also decided that right then and there that it would be theirs and only theirs. Other groups tried, I put it down. Only them. It went on for a good couple of school years sort of under the radar until a year or two ago a couple teachers asked me about it and I told them the story.
Last year was the final year of that group before they went on to other things and late in the school year several things happened with the Mr. Banana, Sir "situation that I thought were interesting and noteworthy.
First, a couple of the kids admitted that they not only knew me by the nickname, they ONLY knew me by the nickname and when my real name was used they had to pause to see who it was that was subbing. I was not offended, because that was actually awesome.
Second, I was at an end of the year event when one of the students referred me by the nickname when I overheard a parent say, "Oh, he is Mr. Banana, Sir." That was a moment that could have gone either way. So, I turned, introduced myself and told the story to the parent and another parent or two that was there. They agreed it was sort of awesome. I really like that place.
We are now a few weeks into the school year and those kids have moved on. For the first time in years there is no one using that nickname. It is retired. These things have life cycles after all. But I know that I am looking forward to that one random day I will be at a school or at an event and I will hear nearby, "Hey, isn't that ... Mr. Banana, Sir?"