Pika Xreme
Name: Raichu-Alola
New Stats: 70/100/60/125/95/140
New Typing(if any): Electric/Psychic
Movepool Addition(s): Shadow Ball, Dark Pulse
New Abilities(if any): Surge Surfer, Levitate
Name: Crabominable
New Stats: 120/135/100/80/90/65
New Typing(if any): Ice/Fighting
Movepool Addition(s): Mach Punch, Drain Punch, Ice Shard
New Abilities(if any): Filter / Iron Fist / Anger Point
Niche in OU: Tank, that can either have more power on its STABs or lessen its weaknesses.
Name: Meganium
New Stats: 100/80/125/90/125/70 (590)
New Typing(if any): Grass
Movepool Addition(s): Slack Off, Weather Ball, Thunder Wave
New Abilities(if any): Overgrow / Thick Fat / Flower Veil
Niche in OU: Another tank, but more on the defensive side.
Ludicrousity
Name: Alolan Raichu
New Stats: 75/80/65/130/80/145
New Typing(if any): Electric/Fairy
Movepool Addition(s): Moonblast, Aura Sphere, Ice Beam, Shadow Ball
New Abilities(if any): Surge Surfer/Competitive/Levitate [HA]
Justification: Moonblast because Coverage and STAB, Aura Sphere for some more nice coverage, Ice beam because regular Raichu gets it in this MoU, Shadow Ball for more coverage. Competitive because of the same reason regular Raichu gets it in MoU and Levitate because this thing is literally floating on its tail. Fairy because it just seems like it would be a fairy, with how cute it looks.
Niche in OU: A nice, fast special attacker, with surprisingly good coverage and a good defensive and offensive typing. Don't let it's cute smile fool you. The smile will still be there after ripping your team to shreds.
zerobreaker000
Name: Crabominable
New Stats: 122/144/97/77/107/43 (BST 590)
New Typing(if any): Ice/Fighting
Movepool Addition(s): Slack Off, Drain Punch, Meteor Mash, Knock Off
New Abilities(if any): Fluffy/Iron Fist/Overcoat
Justification: Fluffy is sort of self explainatory; I picked that instead of Fur Coat so it wouldn't be too much of a tank, though given how many weaknesses Ice/Fighting has it might not even be necessary. Same deal with Overcoat. Slack Off is somewhat symbolic - "It aimed for the top but got lost", from the pokedex entry, so it can be interpreted as it ending up slacking off instead of fighting. Meteor Mash is Comet Punch in japanese, so... good enough? it also lets it fight against fairies. The stat spread gives it a lot more bulk and slightly more Atk, but it's still as slow as ever so that balances out.
Niche in OU: Nice counter to physical ground types, only really fearing Fire-type moves and can easily destroy them with Ice Hammer. Also has Slack Off and Drain Punch for self-sustaining, though any fire-type would destroy it.
Name: Alolan Ninetales
New Stats: 88/67/75/106/135/119 (BST 590)
New Typing(if any): Ice/Fairy
Movepool Addition(s): Wish, Destiny Bond, Water Pulse, Ominous Wind
New Abilities(if any): Snow Cloak/Magic Guard/Snow Warning
Justification: Wish ties into (Alolan) Ninetales' mythical basis, as does Magic Guard. Destiny Bond comes from it laying curse on those who grabs its tail, Water Pulse and Ominous Wind are just generic coverage moves - note that a lot of weird things get Water Pulse, so as long as you aren't a Fire-/Rock-type, you should be fine.
Niche in OU: Fast supporter that scares away every single dragon, I suppose? Now with extra Destiny Bond to take out key threats, and Wish passing for teammates and self recovery. It also gets bulky enough that it should be able to survive a non-steel special attack before setting up.
david0895

Name: Raichu-Alola
New Stats: 70/85/80/135/95/110 (BST 575)
New Typing (if any): Electric/Psychic
Movepool Addition(s): None
New Abilities (if any): Surge Surfer / Levitate (HA)
Justification: Levitate because is literally floating on its tail
Niche in OU: Fast special attacker
Name: Ninetales-Alola
New Stats: 83/67/85/101/110/119 (BST 565)
New Typing (if any): Ice/Fairy
Movepool Addition(s): None
New Abilities (if any): None
Justification: Enough stats for being used in OU
Niche in OU: Fast supporter and revenge killer
Name: Crabominable
New Stats: 97/132/77/62/67/65 (BST 500)
New Typing (if any): Ice/Fighting
Movepool Addition(s): Drain Punch, Ice Shard, Thunder Punch, Knock Off
New Abilities (if any): Hyper Cutter / Iron Fist / Slush Rush (HA)
Niche in OU: Hail sweeper
Name: Meganium
New Stats: 80/82/100/133/100/80 (BST 575)
New Typing (if any): Grass/Fairy
Movepool Addition(s): Moonblast, Weather Ball
New Abilities (if any): Overgrow / Chlorophyll (HA)
Justification: Don't tell me that it's not a fairy...
Niche in OU: Sun Sweeper
Speny
Name: Raichu-Alola
New Stats: 80/85/50/115/95/145 (BST 570)
New Abilities: Surge Surfer, Galvanize, Gluttony
Movepool Additions: Aura Sphere, Trick, Hypnosis, Hyper Voice
Justification: Being a fast psychic type that can volt switch allows for a lot of support opportunities. Also Gluttony because it's theorized that a change in it's diet led to the Alolan form.
Niche in OU: Allows to play the role that it used to better with out out shining Topu Koko but now gets more access to more ways to support the team.
Name: Ninetales-Alola
New Stats: 93/67/75/116/100/119 (BST 570)
New Abilities: Magic Guard, Fluffy, Snow Warrning
Movepool Additions: Recover, Psychic, Wish, Shadow Ball
Justification: Fluffy snow fox.
Niche in OU: Better at surviving and support. Fast hail setter.
Name: Crabominable
New Stats: 97/132/117/62/67/43 (BST 518)
New Abilities: Contrary, Skill Link, Fluffy
Movepool Additions: Ice shard, Bullet Punch, Pin Missile, Icicle Spear
Justification: I messed around with Contrary in ABCAB and it is really fun. Skill Link because it can shoot it's pincers.
Niche in OU: Slow tank that can boost with contrary Superpower and Hammer Arm but lacks Special Defense and has a poor defensive typing.
*Can't use Close Combat with Contrary.
Name: Meganium
New Stats: 100/82/120/123/80/80 (BST 585)
New Abilities: Overgrow, Thick Fat
Movepool Addition: Calm Mind, Psychic, Flamethrower, Flame Charge
Justification: It's a Calm Floral Dinosaur.
Niche in OU: Bulky Thick Fat user with a strong offensive presence.
transwiththeplans
Name: Crabominable
New Stats: 100/150/90/70/90/90
New Typing: Fighting/Ice
Added Moves: Mach Punch, Ice Shard, Bullet Punch, Drain Punch, Meteor, Pin Missle
Abilities: Slush Rush/Iron Fist (Adaptability)
Justification: The Pokedex entry says a Crabrawler adapted to the cold winter mountains, explaining it's hidden ability. Slush Rush for speed. Meteor Mash and Pin Missile also adds to its lore of punching abilities and launching its own pincers.
Niche in OU: Can provide better bulk and potentially revenge kill and sweep with Hail up
Hourai
Name: Ninetales-Alola
New Stats: 90/67/85/110/120/118 (BST 590)
New Typing:Ice/Fairy
Movepool Additions: Calm Mind, Hyper Voice, Wish
New Abilities(if any): Refrigerate (Snow Warning)
Justification: Calm Mind is because the Pokedex states that it is very calm, and Refrigerate is because the Pokedex also states that anyone who angers it will be instantaneously frozen. Wish also references its calm demeanor, and is fitting for a Fairy type that isn't evil.
Niche in OU: Fast Calm Mind/Nasty Plot abuser with amazing Special bulk and okay physical bulk.
swaggron711
Name: Meganium
New Stats: 80/50/130/120/120/80 (BST 590)
New Typing: Grass/Fairy
New Abilities(if any): Overgrow, Thick Fat
Movepool Addition(s): Calm Mind, Power Gem, Moonblast, Psychic
Justification: Thick Fat helps it become neutral to Fire and Ice which it's really weak to. Power Gem helps deal with it's Bug and Flying weakness! Psychic is for dealing with the nasty 4x Poison weakness. Its dex entry states how it revives dead flowers justifying the Fairy type.