So Scarlet (one of my characters) has this problem, a mix-up with her genetics, that cause the gases normally associated with firebreath to sometimes start building up in excess within her body. It mostly shows in her belly and tail, but if let build long enough her entire body begins bloating up. Either way, it makes walking kind of a pain. Plus, the only way to really vent it is to find a safe place to belch out quite a bit of firebreath.
As you can imagine, there's not many places where "safe" and "fire" go together in civilized society. So sometimes things just act up inside while she's, say, out for a walk, and she winds up having to deal with a rather "big" problem.