A simple "Before and after" showing what the art from the gift I drew (here) looks like with and without the belly I drew separately, and not partially obscured by the other character.

Also, I just noticed he doesn't have a bellybutton when he's smaller. An oversight since I knew he was going to be covered up anyway.

And the great thing about this, is you can imagine the belly is filled with anything! Overstuffed with food, Overinflated with air, water, or helium, even pregnant with an absurdly large litter of kits! (I really doubt that last one, but still a possibility for those of you who are into that kinda thing.)