Jon makes comic strips for a living (usually this isn`t shown, though). He has had Garfield as a pet/tormentor since the very first strip in the series, and Odie a little less longer.
Jon has many hobbies that Garfield finds very irritating. Like organizing his sock drawer, dancing the polka and counting the hair from his feet and arms (this has been seen only once, though).
He also has a very interesting wardrobe. Multi colored, stripesy, overly big clothes and ties that squirt water, electrify, spin etc, which annoy Garfield very much.
Jon is a very hated man. He has gotten eviction notes that tell him to move away from USA and Planet Earth, is not a faforite of Garfield (but then again, he cuts Jon some slack, sometimes), women find him repulsive etc. He also has bad luck, which explains why he stayed as a miserable single for so long. Even if he had a date, his dates are totally weird, such as Bertha, who is obese or Kimmy, who was raised by wolves, and Felicia who was allergic to cats.
But after years and years (decades), Dr. Liz Wilson, Jons long time crush, started to date him. They haven`t broke up yet. And due to the laws of comic strips, probably never will.
Jon also has very bad cooking skills and makes the most weirdest cuisine ever including moose soup with chocolate sauce. He is sometimes disorganized as his fridge is filled with rotten food.
Created by Jim Davis.