What are all of the Pokemon that have different forms?

Question

I know that Arceus, Deoxys, Shaymin, Giratina, Rotom, Shellos, Gastrodon, Pikachu (the different ones in costumes), Gyarados, Meloetta, Kyurem, Keldeo, Genesect, Furfrou, Hoopa, Tornadus, Thundurus, Landorus, Scatterbug, Spewpa, Vivillon, Darmanitan, Greninja, Pyroar, Meowstic, Minior, Aegislash, Pumpkaboo, Floette, Minior, Wishiwashi, Lycanroc, Solgaleo, and Lunala have different forms, but can someone tell me what all of the Pokemon that have different forms are? Please include regional variants, changes in appearance during moves, fused Pokemon, Pokemon that change forms when holding or using items, gender variants, and anything else that I forgot.

-Thanks

Comments

Only Vivillon has different forms, Scatterbug/Spewpa remain the same.

---

Anime says Scatterbug has different patterns as well.

Answer 1

This list ignores shininess and doesn't include gender differences if the only difference between the genders is their interactions with infatuation or captivate.
Mega evolutions: Venusaur, Charizard, Blastoise, Alakazam, Gengar, Kangaskhan, Pinsir, Gyarados, Aerodactyl, Mewtwo, Ampharos, Scizor, Heracross, Houndoom, Tyranitar, Blaziken, Gardevoir, Mawile, Aggron, Medicham, Manectric, Banette, Absol, Garchomp, Lucario, Abomasnow, Beedrill, Pidgeot, Slowbro, Steelix, Sceptile, Swampert, Sableye, Sharpedo, Camerupt, Altaria, Glalie, Salamence, Metagross, Latias, Latios, Rayquaza, Loppuny, Gallade, Audino, Diancie
source
Alolan Forms: Rattata, Raticate, Raichu, Sandshrew, Sandslash, Vulpix, Ninetales, Diglett, Dugtrio, Meowth, Persian, Geodude, Graveler, Golem, Grimer, Muk, Exeggutor, Marowak
source
Caused by abilities in-battle: Castform, Cherrim, Darmanitan, Greninja, Aegislash, Zygarde, Wishiwashi, Minior, Mimikyu
Caused by items: Groudon, Kyogre, Giratina, Arceus, Genesect, Silvally
Caused by moves: Keldeo, Meloetta
Caused by evolution conditions: Wormadam, Lycanroc
Changeable outside of battle: Pikachu, Deoxys, Rotom, Shaymin, Tornadus, Thundurus, Landorus, Kyurem, Hoopa, Oricorio
Determined upon encounter and unchangeable: Pikachu, Basculin, Floette, Meowstic, Pumpkaboo, Gorgeist, Zygarde
Completely aesthetic: Pichu, Unown, Burmy, Shellos, Gastrodon, Deerling, Sawsbuck, Vivillon, Flabebe, Floette, Florges, Furfrou, Xerneas, Minior, Solgaleo, Lunala
source

Comments

Hey what about Keldeo? He should be with Meloetta in Caused by moves.

---

I classified Keldeo as "completely aesthetic".

---

Didn't see that sorry.

---

On second thought, Keldeo's form isn't completely aesthetic because it reveals secret sword.