Question

If Shedinja used a Physical move on a Yamask or Cofagrigus, would it be affected by Mummy?

Answer 1

Multitype, Wonder Guard and Mummy itself are the only Abilities not affected by Mummy.

Source: Bulbapedia/ Mummy

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Nothing would happen.

Answer 2

After taking damage from a Direct Attack, changes the attacker's Ability to Mummy. (Does not affect Wonder Guard or Multitype.)

Source by marriland.com