The BeerBelly Rabbit was never a fat guy. He was actually pretty thin most of his adolescence.
But then he got this job he was really proud of, where he earned a lot of money and also got to wear a tie every day :)
And after work, he went to get a beer with his buddies, as he felt the need to socialize, but didn't have the strenght to think of anything else or do something more than sit on a chair and move his paws up and down, mouth to table.
So in a few years he discovered this protuberance where his stomach once was. A beer belly. Cute, right? :)
That's why he now wears his tie on the side, so everybody can see his beer belly and instantly get it: he's a hard-working rabbit, that's his only joy :)