Stats:
HP- 55
Attack- 90
Defense- 80
Sp.Atk- 50
Sp.Def- 105
Speed- 96
Type
Ghost/Fairy
Ability(s)
Disguise: Nulls one direct attack once per battle.
Overview
Don't let Mimikyu's low stats fool you, it's deceptive in more ways than both its types imply. Its signature ability, Disguise, really makes this Pokemon a unique threat all by itself. This ability, along with it's three type immunities to Dragon, Fighting, and Normal, and all the switches it forces, gives Mimikyu plenty of opportunities to get in unharmed and start setting up. It's movepool isn't too impressive, but it gets just what it needs to be abuse those free turns. It only ever often needs Play Rough and Shadow Claw to cover most prominent Pokemon, and having Shadow Sneak is just icing on the cake. Not only that, it gets Swords Dance, which it can set up really easy thanks to how many opportunities it gets to switch in for free. It also has good defensive utility with moves like Bulk Up, Taunt, Will-O-Wisp, Pain Split, and Substitute.
It does suffer from several things, however. The ability does not prevent status, not even from the Scald's burn chance, and thus is very vulnerable to burns and Toxic. It's bulk is under average at best, and once its disguise is down, can easily revenge killed on most variants. Another problem is its stats are low and without setting, it's power is very mediocre. It's easily out sped as well, as 96 Speed isn't that impressive. Mimikyu also lacks immediate power, relying on set up moves to be threatening. On top of that, if you go Adamant, you miss outspeeding key threats, but if you go Jolly, it loses some power and thus misses out on some KOs. But if you play Mimikyu smart and to its strengths, it can really pack quite a punch to any team.
Swords Dance
~Swords Dance
~Play Rough
~Shadow Claw
~Shadow Sneak/Substitute
Item: Life Orb/Red Card/Pixie Plate/Spooky Plate
Nature: Adamant/Jolly
EVs: 252 Attack, 252 Speed, 4 Defense
Ability: Disguise
This is probably Mimikyu's best set. This takes advantage of all the free turns it can score by setting up a Swords Dance or two before beginning to take enemies down. This set works especially well as a revenge killer, and can sometimes even begin to sweep, especially mid to late game. Play Rough and Shadow Claw are STAB, while Shadow Sneak can help catch speedier weakened prey. Another option over Shadow Sneak is Substitute, which allows it to absorb status and give it more chances to clean up house.
Life Orb gives it maximum power and flexiblility, making it hit like a truck after one Swords Dance alone. Since Mimikyu is immune to one Attack per turn, Red Card allows for Mimikyu to directly counter set-up sweepers once by forcing them out. If you want extra power but no recoil, Pixie or Spooky Plate work as decent replacements, especially if you're running Substitute. Adamant nature ensures it hits as hard as possible, while Jolly notably lets you outspeed Timid Xurkitree and Timid Tapu Lele not running Choice Scarf.
Bulk Up
~Bulk Up
~Play Rough
~Shadow Sneak/Shadow Claw
~Will-o-Wisp/Substitute/Taunt/Pain Split
Item: Leftovers
Nature: Careful
EVs: 252 HP, 252 Sp.Def, 4 Defense
Ability: Disguise
Again taking advantages of the free turns it can score, while also taking advantage of its high Special Defense, Mimikyu can use it to start setting up Bulk-Up, making it harder to kill the more it sets up. This set sacrifices power for staying power. Shadow Sneak is needed especially because of the fact this set runs no Speed EVs, but Shadow Claw still works here as well if stronger Ghost STAB is needed. The last slot can go to Will-O-Wisp, which makes it even more bulky on the physical side. Substitute also works here because of all the status setters it invites. Taunt helps deal with other slower taunts as well as defensive Mons trying to ruin your work out with their taunts, burns, or just walling you with recovery. Pain Split is the only reliable recovery it gets, and with its low HP, can take full advantage of it.
Other Options
Not much. While it's glitched on Pokemon Showdown, in the real game, Weakness Policy does NOT activate when Mimikyu is hit with it's disguise up. Toxic can be slapped on either set, which allows it to wear down potential switch ins that may otherwise wall it. Oddly enough, it gets Wood Hammer, which can be used to get rid of common bulky Water types, but fitting this in Mimikyu's sets is difficult. On the Swords Dance set, Ghostium-Z is an honorable mention as it allows for Mimikyu with one Swords Dance set up to 2HKO some walls, notably max Defense Toxipex, that otherwise stop your sweep cold. But this comes at an opportunity cost for your team, and dents Mimikyu's power somewhat outside this situation. A stall set with Toxic/Will-o-Wisp, Substitute, Protect, and Pain Split has a niche. But I personally feel that this is an underwhelming set that isn't as effective once Disguise is gone. It learns Thunder Wave, which can replace Will-O-Wisp on the Bulk Up set, which can help it better deal with speedy switch ins
Counters
While Mimikyu can be hard to deal with, especially offensive teams, it can still be beaten. They key is primarily prevent it from setting up, as without setting up, it fails to be threatening. Fast Taunt users come to mind for this job. Unaware Clefable and Quagsire ignore any of Mimikyu's boost and proceed to hurt or cripple it without fear of anything but maybe a burn or the occasional Toxic. Burns and Toxic cripple Mimikyu itself, as status goes through Disguise and put a timer on how much it can do. Mold Breaker Exadrill can ignore Disguise and proceed to KO it. Speaking of Steel, many Steel walls such as Ferrothorn, Skarmory, and Celesteela can take most of what Mimikyu has to offer and wear it down through Disguise, or just KO it with STAB Steel moves. Skarmory can also Whirlwind Mimikyu away, even behind a substitute, as can Hippowdon. Toxapex gets a special mention, as without Ghostium-Z boosted Shadow Claw, Toxipex can either Haze Mimikyu, set up Toxic, or burn it with Scald. The newly buffed Mantine can also take a hit and Haze it's boosts away, as well as burn it and take away Disguise.