how to spella Mississippi

lol!

It also reminded me of an interesting conversation I had with a sweet friend I used to talk to all the time... this joke seems ideal to read on the page, working better than if narrated vocally (FTF) Is there a word for this phenomenon of humour that is orthographically based, which is sometimes even a kind of sight-gag pun?

and if not, what shall it be henceforth? ;)