Mimikyu as a Check on Fairy
Mimikyu @ Mimikium Z
Ability: Disguise
EVs: 252 Atk / 4 SpD / 252 Spe
Adamant Nature
- Play Rough
- Shadow Sneak
- Shadow Claw
- Swords Dance
AV Set
Just preserve Mimikyu's Disguise and switch in safely on Muk-Alola when a teammate get defeated. After putting Mimikyu in front of Muk-Alola, just use Swords Dance + Let's Snuggle Forever or just use Let's Snuggle Forever + Play Rough and it's all over.
Curse set
Uh, that's a complicated set. Mimikyu can't check this Muk-Alola set after one curse boost, which means that it has to switch in without any defense boost, being able to just Swords Dance and use Z-Move, killing it. That is possible pressuring Muk-Alola with your teammates, forcing it to Poison Jab, avoiding giving chances to it to use Curse. (Mimikyu can switch in on one Poison Jab at full life with Disguise up. If Poison Jab poison it, or just get two high rolls, then your Mimikyu will get defeated and you can't do too much about this.)

Mimikyu @ Mimikium Z
Ability: Disguise
EVs: 252 Atk / 4 SpD / 252 Spe
Adamant Nature
- Play Rough
- Shadow Sneak
- Shadow Claw
- Swords Dance
AV Set
Just preserve Mimikyu's Disguise and switch in safely on Muk-Alola when a teammate get defeated. After putting Mimikyu in front of Muk-Alola, just use Swords Dance + Let's Snuggle Forever or just use Let's Snuggle Forever + Play Rough and it's all over.
Swords Dance + Let's Snuggle Forever
+2 252+ Atk Mimikyu Let's Snuggle Forever vs. 248 HP / 12 Def Muk-Alola: 660-777 (159.8 - 188.1%) -- guaranteed OHKO
Easy Kill
Let's Snuggle Forever + Play Rough
252+ Atk Mimikyu Let's Snuggle Forever vs. 248 HP / 12 Def Muk-Alola: 331-390 (80.1 - 94.4%) -- guaranteed 2HKO
252+ Atk Mimikyu Play Rough vs. 248 HP / 12 Def Muk-Alola: 157-186 (38 - 45%) -- guaranteed 3HKO
+2 252+ Atk Mimikyu Let's Snuggle Forever vs. 248 HP / 12 Def Muk-Alola: 660-777 (159.8 - 188.1%) -- guaranteed OHKO
Easy Kill
Let's Snuggle Forever + Play Rough
252+ Atk Mimikyu Let's Snuggle Forever vs. 248 HP / 12 Def Muk-Alola: 331-390 (80.1 - 94.4%) -- guaranteed 2HKO
252+ Atk Mimikyu Play Rough vs. 248 HP / 12 Def Muk-Alola: 157-186 (38 - 45%) -- guaranteed 3HKO
Curse set
Uh, that's a complicated set. Mimikyu can't check this Muk-Alola set after one curse boost, which means that it has to switch in without any defense boost, being able to just Swords Dance and use Z-Move, killing it. That is possible pressuring Muk-Alola with your teammates, forcing it to Poison Jab, avoiding giving chances to it to use Curse. (Mimikyu can switch in on one Poison Jab at full life with Disguise up. If Poison Jab poison it, or just get two high rolls, then your Mimikyu will get defeated and you can't do too much about this.)
+2 252+ Atk Mimikyu Let's Snuggle Forever vs. +1 248 HP / 12 Def Muk-Alola: 441-520 (106.7 - 125.9%) -- guaranteed OHKO after Stealth Rock
0 Atk Muk-Alola Poison Jab vs. 0 HP / 0 Def Mimikyu: 109-129 (43.4 - 51.3%) -- 5.9% chance to 2HKO
0 Atk Muk-Alola Poison Jab vs. 0 HP / 0 Def Mimikyu: 109-129 (43.4 - 51.3%) -- 5.9% chance to 2HKO