How can I turn a player into a model?

Well I really want to know like If you have a model when people play your game a gui can pop up and when then click it they turn into a that model how can I do that?

Let's say you want to make a model of yourself. You press Test then Play solo. Then if you go to workspace you willl see a model called player 1. The player 1 is you. Then you save it.