No, there isn't a "Pokemon Duplicator" in any game. Plus Feraligatr is not available in Pokemon Red, obviously.
However, there is a cheat - you could clone Pokemon in Red/Blue, when doing a cable trade. You turn off the Gameboy power just after the game has shown the Pokemon being traded, but while it's still saving. The Pokemon of the person who hosted the trade gets saved over their friend's Pokemon, but their friend still gets the traded Pokemon.
If you're playing on an emulator or something then it is very unlikely to work. I think your friend is lying.
