Mr. Saturn (どせいさん, Dosei-san) is an item that appears in Super Smash Bros. Melee and Super Smash Bros. Brawl. It walks around the stage, pushing other items along with it. It also cries when making contact with an opponent. If thrown, it will deal very little damage and knockback, but it can be used repeatedly, as it does not disappear after one use. As an unconventional meteor smash, Mr. Saturn gives off a large amount of stun when it hits an opponent, making it great for combos. It also does a significant amount of shield damage—21 in Melee and 42 in Brawl.
In Super Smash Bros. Melee, there are various bonuses related to Mr. Saturn.
In Super Smash Bros. Brawl, Lucas makes his entrance riding in on the Mr. Saturns' coffee table.
 Damage table
In Brawl, the momentum of a projectile will affect the damage a character will receive; these are recorded in bounces.
Note: A Mr. Saturn cannot be dropped while on the ground; the player will throw it instead.
Mr. Saturns made their first appearance in EarthBound. Mr. Saturns are strange creatures that reside in Saturn Valley where they provide health care and hotel stays free of charge, while other towns charge more and more as the game progresses. They also have their own eccentric dialect that involves saying either "Zoom", "Boing", "Ding", or the occasional "Dakota" at the end of their sentences. Mr. Saturn also speak in a very distinctive typeface. In an interview with Shigesato Itoi (director of the Mother series), Itoi states that Mr. Saturns are the "symbol of innocence". Mother 3 also features Mr. Saturns, who behave the same way as they did in EarthBound. In Melee and Brawl, Mr. Saturns simply walk around until they disappear and can be picked up and thrown at other players. Mr. Saturns having a passive attitude in Melee and Brawl could be a reference to how they're the "symbol of innocence", and the cry that Mr. Saturns make when thrown at another player is likely a reference to their eccentric dialect in EarthBound and Mother 3. 
 Super Smash Bros. Melee
The origins of the Mr. Saturn race are unknown. But many belive that they come from outer space. They are found in Saturn Valley and speak their own unique language. In Super Smash Bros. Melee, Mr. Saturn is just another item with which to pelt foes. These guys are laid back and not into fighting, so you can rest easy... or can you?
 Super Smash Bros. Brawl
A creature from a race of unknown origin that speaks its own unique language. Some say they came from outer space, but the facts behind their appearance are wrapped in mystery. In Smash Bros., they'll wait a bit after appearing before wandering off on their own. They can be picked up and thrown at foes for minimal damage. Their shield-breaking properties are high.