What are all the species that are impossible to obtain Shiny through legitimate means?

Question

What shinies cannot be obtained? I know the legendary galar birds couldn't be shiny before.

Comments

To be fair to this question, the original post is about individual shinylocked Pokemon. This one can be referring to totally illegal even counting events.

---

Re-opened with new title.

---

I can't believe this question hasn't been asked before

Answer 1

There's two ways a Pokémon can be impossible to obtain as a Shiny. Either it's restricted to an Event (which usually never appear Shiny) or the Pokémon is only obtainable in-game, but is Shiny Locked there.

With that criteria, the following Pokémon can not be obtained in their Shiny forms through any legitimate means:

Ash Hat Pikachu (this includes every single form ranging from Kanto, Johto, Hoenn etc.)
Victini
Keldeo
Meloetta
Ash-Greninja (regular Greninja can still be Shiny, but the Event Greninja with Battle Bond is Shiny locked)
Hoopa
Volcanion
Cosmog
Cosmoem
Magearna
Eternatus
Kubfu
Urshifu
Zarude
Glastrier
Spectrier
Calyrex
Enamorus
Vivillon (Fancy Pattern)
Vivillon (Poké Ball Pattern)
Moltres-Galar
Dialga (Origin Forme)
Palkia (Origin Forme)

Source

Hope this helps!

Comments

Shiny Melmetal is (or rather, was) obtainable as shiny meltan could be caught and evolved in Pokémon GO. The shiny Melmetal can then be transferred to the main series. Also, the QR code Pikachu in USUM can be shiny, despite the shiny looking identical to a normal one.

---

I remember hearing somewhere that pokeball color magearna can be shiny

---

Once pla transfers can be back origin forme d and p will be shiny able and in a few weeks galarian moltres