Flinch

Flinching is when a character's current action is interrupted by being attacked and replaced with a short animation of being hit. The knockback dealt affects how strong the flinch is - weak attacks incur only a few frames of flinching, while stronger ones can deal about three times as much (and for some characters, even more if their legs are struck), but those strong enough to cause tumbling skip the flinch animation altogether. As a result, attacks that do not cause any knockback will not cause flinching, and neither will attacks that deal no damage.

As flinching is directly related to knockback received, reducing knockback through a sticker, increasing weight through a Super Mushroom or Metal Box, or using a move with launch resistance will also make it more difficult to flinch.

Flinching while charging an attack or special move will cause the charge to be lost, regardless of whether any charge had been saved previously. Mewtwo does not lose its projectile's charge if it flinches, though this is only the case for when it is about to fire the projectile, not while it is actually charging.