My friend told me that in BW2, if you go into the Hidden Grotto in Pinwheel Forest and find a Bagon, then it will be Shiny. I don't believe him at all, but just to reassure: Is this really true???
>Pokémon in the Hidden Grotto cannot be shiny and the contents are set when regenerated, they cannot be soft reset.
No.
source
I checked on some websites before posting just to ensure. Your friend is totally lying...as it is impossible to find a shiny Pokemon in any grotto without cheats-but ya.