Stun

Mario stunned by Wario. A Gooey Bomb has been placed on him as well.

Being stunned is a special condition that leaves a character immobile for a short period of time. The most common way a character can become stunned is by shattering their Shield. When a character is stunned, they will be dazed for a few seconds and won't be able to move or attack. The only way for a character to snap out of this condition is through an attack of another character (unless the attack does not cause flinching) or waiting out the condition. A character can shorten the amount of time that they are stunned by button mashing. Also, bigger characters have lower stun times.

Unlike most other status effects, characters can escape being stunned easier at higher percentages (whereas sleep, for example, lasts longer at higher percentages). The sound effect of being stunned is a cartoonish tweet sound effect that loops until the condition is stopped immediately. In Brawl, the sound was less cartoonish than in SSBM. The sound effect does not play if the character has taken very heavy damage. It depends on the percentage of damage taken.

Origin

In the Mario Party Series, if the player is affected by dangerous areas or hazards they will feel dizzy. The "tweet' sound effects play while he/she is in this condition.

Causes of Stunning

• Shield shattering - When the character's Shield shatters from overuse of it, the character will be stunned for a short period of time.
• Reflector shattering - Reflectors slightly increase the power of what they reflect. If the same thing is reflected multiple times, the Reflector can be overloaded and shatter like a shield.
• Disable - Mewtwo's Disable causes stunning if eye contact is made with it.
• Deku Nut - A new item introduced in Super Smash Bros. Brawl, when the Deku Nut is broken, all the grounded characters in the blast radius will be stunned. The Deku Nut will break on its own when not used for a period of time.
• Weavile's False Swipe - Weavile will slash across the stage using its False Swipe move. Any grounded character that makes contact with Weavile's False Swipe will be stunned momentarily. If the player is caught in the attack, it can very difficult to avoid being hit again.
• Wario Waft - When Wario-Man does a barely charaged Waft, it briefly stuns opponents.
• Negative Zone - Among other things, exposure to Luigi's Negative Zone can stun opponents. If the character is in mid-air while the Final smash is active, they will fall back to the ground and will be stunned (thus, being automatically done with a Shield Break).