Being stunned or dazed (referred to as FuraFura in Super Smash Bros. Melee's debug menu and in-game files for Brawl, after the Japanese onomatopoeia for dizziness), an effect known as dizziness in Brawl, is a special condition that leaves a character immobile for a short period of time.
When characters are stunned, they are dazed for a few seconds and cannot perform any actions. The only ways for a character to recover is by flinching, waiting out the condition, or by button mashing to reduce duration.
Unlike most other status effects, characters can escape being stunned easier at higher percentages (whereas asleep, for example, lasts longer at higher percentages). In Smash 64, the base time in frames that a character is stunned can be determined by the formula (400-damage)+60.
The sound effect of being stunned is a cartoony tweet sound effect that loops until the condition is stopped. This sound effect debuted in Melee, and its volume was increased in Brawl. In both games, characters also have a flashing red overlay applied to their model; in Smash 4, however, this only happens when a character's shield is broken.
Causes of Stunning