Mr. Saturn (どせいさん, Dosei-san) are a friendly species of characters in Mother 2/EarthBound, as well as its sequel Mother 3. They are found primarily in the Saturn Valley portion of Eagleland. They resemble large heads with feet, an oversized nose, cat-like whiskers and a bow on a single hair. They speak in a unique font used only with them. They generally end their sentences with words such as "boing" and "zoom". It was revealed the font used on the Mr. Saturn in the Japanese version was inspired by Shigesato Itoi's daughter's handwriting at the time. In addition, they all are identical and called Mr. Saturn, save for the doctor, Dr. Saturn. According to Itoi, the Mr. Saturn race are a symbolism of innocence in the games.
During the events of EarthBound, the party is brought to Saturn Valley. Many Mr. Saturn have been kidnapped by the forces of Giygas, the primary antagonist in the game, and been forced to work in a factory. They produce Fly Honey for a sentient pile of sludge known as Master Belch. Ness, Paula, and Jeff liberate the Mr. Saturn after defeating Master Belch. Later in the game they assist Dr. Andonuts and the Apple Kid in making the Phase Distorter the party uses to reach Giygas for the final confrontation.
The Mr. Saturns once again appear in Saturn Valley, this time located in the Nowhere Islands. The Pig Mask Army have taken over the valley looking for information about the seven needles. Lucas, Kumatora and Boney rescue several Mr. Saturn from being tied up by a Pig Mask Lieutenant, as well as their friend Duster, who had been separated from them. After saving them, the Mr. Saturns reveal that they do know where the needle is, and proceed to take Lucas to it.
Once again, the Mr. Saturns show technological skill. They've modified a Pork Bean transport, as well as created the Saturn Rider. After the Pig Masks destroy the exit from Saturn Valley, they help Lucas make a flying device with birds and a cage. One of them takes the Badge of Courage from Lucas to polish it. When he returns it, it is revealed that it was a Franklin Badge.
Super Smash Bros. series
Beginning in Super Smash Bros. Melee, Mr. Saturn are available as an item. They appear on the stage and walk around for a bit. If they are picked up they can be thrown as a projectile, though they cause minor damage and no knock-back. In addition, they can occasionally break shields. They reappear in Super Smash Bros. Brawl with the same role. Also, Lucas's entrance is the Saturn Rider, a Mr. Saturn shaped coffee table that can be ridden like a horse, from Mother 3.
"The origins of the Mr. Saturn race are unknown, but many believe they came from outer space. They reside 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. Melee)
"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." (Super Smash Bros. Brawl)
Mr. Saturns is one of the more iconic elements of the Mother series, which has led it to be great in marketing. Mr. Saturn merchandise is particularly popular in Japan. They have appeared as plush toys and figurines, as phone straps and phone cleaners, and as keychains and stickers. The Mother 1+2 Mr. Saturn Book came with a Mr. Saturn figurine.
In Kirby Super Star Ultra, you can find Mr. Saturn as a treasure.