Magic beans that live in your computer, or, uh, digital Chuck E. Cheese tokens. On a side note did you know the E. stands for Entertainment? Entertainment is literally that mouse’s middle name.
Isn't all fiat money magic in that way?
Nope. Fiat money is created as debt repayable only in that currency, and backed by a government which levies taxes only in that currency, so future demand to obtain the currency doesn't depend entirely on the assumption its purchasing power will go up. Even then, it needs a lot of intervention to keep it stable on a day to day basis.