In the real world, we used fiat or physical money in our daily spending. And this physical notes can be use in fraudulence or a so-called Fake Money.
How about in Cryptoworld, is there also a Fake Bitcoin? If there's any, how can we identify it?
Al altcoins are Facke bitcoin, because they take the bitcoin source code and create new coins.
All the Forks are fake bitcoin too because they take the main blockchain and split it while getting a new coin.
Even we have fake satoshis, some users claiming they are satoshi. So, just don't believe everything you read

I wouldn't say that altcoins are fake Bitcoin because they use the same source code. They are varieties of crypto they just use the same technology and source. They would be fake when some coins would claim to be Bitcoin and use the same name and they are not, which is possible only in theory because in real life this would be revealed instantly.