The toner is then fused onto the paper using heat, pressure, or a combination of both. Most modern photocopiers use a technology called xerography, a dry process that uses electrostatic charges on a light-sensitive photoreceptor to first attract and then transfer toner particles (a powder) onto paper in the form of an image. If you could achieve this, there is no danger to use whatever you want, even staples.A photocopier (also called copier or copy machine, and formerly Xerox machine, the generic trademark) is a machine that makes copies of documents and other visual images onto paper or plastic film quickly and cheaply. The most important thing in your work is to secure the insulation, ensuring you will not destroy it in any way, both during construction and later. If this is not good in your case, consider using as a holder something that is an insulator and which is large enough to not move within a box, like a properly cut piece of plastic or wood (large enough to not move loosely, but possible to take away if you need to repair the toy). In your case I would consider gluing the wire to a base, either with a glue or a tape. This deformation should not be a risk with low voltages (you say you are constructing a game so I do not expect anything higher than 30 Volts), but can be for higher voltages. It is also necessary you will not destroy the insulation when inserting a holder.

A staple (or a nail, a screw etc.) uses force to keep the wire stick and this force can deform the insulation. There is no problem to use staples (or other metal things like nails), but there is always a risk you will destroy insulation of the conductor, which may eventually lead to a short-circuit.

Print conductor staple