Are all event Pokemon giveaways programmed not to be shiny?

Question

Besides the one for the legendary dogs.

Answer 1

It is impossible to get a Shiny Mystery Gift Pokémon, UNLESS it is meant to be Shiny like the Pikachu-colored Pichu. This is because in the game's coding, there is a Shiny check function which prevents Mystery Gift from being Shiny by regenerating a new PID until the Pokémon isn't Shiny.

Source: Bulbapedia