You can expand those little condiment cups you get from fast food joints so they can hold more ketchup and stuff. I didn't know that and thought it was neat.
Those sauce cups (the kinds you see in some diners and fast food joints) are made with an almost-circle of paper, with an adjustable paper rim. The circle 'cup' is folded in such a way, that it can be partially unfolded with a little pressure. The same with the rim... it's overlapped and folded, then rolled, which allows it to expand when pulled. So, if you gently pull around the edges, you can expand the cup, almost (or possibly more than) doubling its volume/capacity.
I have a girlfriend. This is a breakthrough in ketchup science, now I don't have to carry 4 little cups of ketchup..
In some parts of the world, they give you one ketchup packet that has like 20ml in it or something. Whatever it is, it's like 4 or 5 of the dumb fucking little ones we have here. It's way better.