Assuming you are playing X and Y, no, this is definitely not possible. Whether or not a Pokemon is Shiny in X and Y is determined by the Pokemon's personality values, the trainer's hidden ID number and their normal ID number, with the first two being hidden parts of the game never revealed at all and can only be accessed/changed by hacking the game. Bulbapedia explains this in more detail.
Also, he can't be using PokeGen or Action Replay since neither of them have been released for X and Y, and Pokemon Bank's censors will likely pick up Shiny hacks in you try to transfer them to X/Y that way. However, in previous games, Action Replay codes, PokeGen and some hacks could assist with making a Pokemon Shiny, but this is a really dishonest way of getting a Shiny, and is also technically illegal.
So basically, your friend is lying. That's all there is to it.