lol well i just joined like 12 minz ago so just wanted to drop inn and say hi:D
kk so i have a sun 24’’ idk the model but i was wondering if it was possible to put a fatter 20’’ rim on it … id most likely swap the hub and cranks out aswell
but whats your guys opinion will the geomitry be to far askew or do you think it will work well? 
It is not a bike so it is not going to have bike like geometry issues when you swap out the wheel. everything is in a strait line.
What do you want the fat tire for? If it is to help jumping with the unicycle you should probably look at getting a trials wheelset. They are 19x2.5" (often listed as 20x2.5) wheels which give you the same outside diameter as a regular 20x2.0 wheel.
I am not sure if the the sun frame is wide enough to fit a trails wheelset but if it is you could give it a try.
Personally thought if you are going to be doing upgrades to a unicycle it might make more sense to start with something more middle of the line like a Nimbus or Torker and go from there.
There is a good chance that the frame might brake if you abuse it too much riding it like a trails. Sun unicycles were never designed for that kind of riding.
thnx for the advice
id most likely just get a 19 inch wheel set like you said … im not doing any crazy drops or anything too stressing on it … i just have always liked the feel of a 20’’