I've thought of a type of inflation which isn't used much, and yet opens up some ideas for stories. It coincides with another popular fetish, Shrinking or miniature people.
If you were to put a hose inside yourself and pump once, the air forced inside you wouldn't affect you much. You would have to pump much more air into yourself in order to expand your belly/body, which would take some time.
But if you were smaller, say a foot high, then the same single amount of air pumped inside you would have a much more dramatic effect.
