If a Mimikyu in its Disguised Form is hit by a damaging attack or hits itself in confusion, Disguise prevents the move from calling the damage formula. The move will thus deal no damage, and type effectiveness will not be calculated (except in case of an immunity, which prevents Disguise from triggering since the move will not hit in the first place). When this effect activates, the message, "Its disguise served it as a decoy!" is displayed, Mimikyu changes to its Busted Form, and finally the message, "<Name>'s disguise was busted!" is displayed. If Mimikyu's type had been changed beforehand, it is restored to Ghost/Fairy when it changes to its Busted Form.
Mimikyu remains in Busted Form if it is switched out, but reverts to Disguised Form outside of battle. If a Mimikyu faints and is revived, it will be revived in its Disguised Form and Disguise will be able to activate again.
Because a Disguise-busting hit skips the type effectiveness check in the damage formula, Weakness Policy will not activate regardless of the move's type. A held Air Balloon will be popped even if Disguise negates the damage.
If Disguise is broken by Ice Ball or Rollout, the damage multiplier won't be in effect, but the Ice Ball/Rollout turn count will (ie, doing x16 damage on turn 5). After Rollout/Ice Ball finishes, whatever move used next will do 16× the normal damage, or ×32 if Defense Curl was used.