Well you can consider the numerous forked counterfeit Bitcoin as most have the same circulating/total supply lol. Actually we have fake Bitcoin and they're all the forked out there claiming to be the real Bitcoin which is the reason behind their forking in the first place. Don't forget some Bitcoin address and some of the forks share similar address or exact address (most especially the legacy format addresses) and scammers used this as an advantage to scam victims.
I have had reports of victims receiving BCH (Bitcoin cash or fake Bitcoin) for the price for bitcoin when they transacted peer2peer which is quite possible as most Bitcoin and Bitcoin cash share same address. About the theory of a totally fake Bitcoin like the rumors going around of recent of scammers sending you a fake Bitcoin when you intend transacting peer2peer in my region, that I haven't confirmed but most scenario will be a double spending scams.