- "Dad. It's me. Claus. I told Lucas to come too, but he's been crying at Mom's grave all this time. Dad. I'm gonna leave this apple here. The core might be hard, but... The core... The core might be too hard to eat, but be SURE you eat it! I'm gonna get stronger. ...I'm gonna get so strong even Dragos won't stand a chance against me! Dad... I..."
- — Claus
Claus (クラウス, Klaus in the North American version of Brawl) is a major character in Mother 3. He is a boy from Tazmily Village. Claus is energetic and far more courageous than Lucas. He is last seen by the player lying motionless near the Drago Plateau, although the residents of Tazmily are never made aware of this.
Claus resembles Lucas in every way, except for the color of his clothes and hair. He has a similar hairstyle to Lucas, but he has orange hair, and wears a striped T-Shirt that resembles his brother's; With the colors different. They are Yellow and Cyan. He wears orange pants, white socks and cyan-white shoes.
However, when he is in his masked man uniform, his appearance becomes slightly different. He wears a long yellow shirt instead of his casual short striped shirt, although it cannot be seen very well because of his black-gray coat. However, he still wears his orange pants. He wears black-grayish boots.
- "...Huh? That monster's name is Claus? Its name was Claus?! That almost sounds like a person's name! But now it's my robot. Not even a fragment of life remains inside it. It's Master Porky's slave robot! It does whatever I say! It acts on my will alone. It's my double. It doesn't know anything about who you are! *cough* *cough*"
- — Porky Minch
The Masked Man is the secondary antagonist of Mother 3; a mysterious character who debuts during the final scene of the fifth chapter. He is the only other person besides Lucas capable of removing the seven Needles. He attacks with lightning, a sword, an arm cannon and PK Love. Additionally, he has the ability to destroy PSI Shields and use mechanical wings to fly away. He also has a lightning attack that is able to instantly render Lucas's entire party unconscious, meaning that only himself and Lucas (because of the Courage Badge that was revealed to be a Franklin Badge) remain in the battle. The attack is unavoidable.
The Masked Man works for Porky Minch, the Pig King, as what he refers to as his "adorable little monster," and never says a word in the story onscreen. A Pigmask states to Lucas (who thought he was the Masked Man since he answered his phone) that he sounded "kind of cheery", possibly signalling that the Masked Man can, in fact, talk, though in an emotionless tone. The Masked Man is the final boss of Mother 3, rather than Porky Minch himself. Because of this, Porky has been the penultimate boss in both games he has appeared in.
The Masked Man is in reality, Claus, who was apparently discovered near the Drago Plateau by the Pigmask Army. He was brought back to consciousness and turned into a human chimera. It is unknown whether or not he was dead when found, though the implications point more toward being dead, as the Magypsies sensed no heart in him, and it's also impossible to hear his heartbeat in battle. During this time, Porky used him as a loyal servant and gave to him near full command of the Pigmask Army. While under the control of Porky, Claus's sense of self and memories had been forgotten and pushed deep inside of him.
At the end of the final battle with the Masked Man, after realizing his true identity and revealing himself as Claus, he fires an intense bolt of lightning at Lucas, purposely reflecting it off of Lucas's Franklin Badge, causing himself mortal damage and ultimately killing himself.
The Masked Man has three battle themes. The first music is a variation of "Strong One", entitled "Strong One (Masked Man)". The latter songs that are heard during each portion of the final battle against the Masked Man are titled "Battle Against the Masked Man" and "It is Finished", respectively. "It is Finished" is an eerie, sad rendition of "Mother 3 Love Theme". During the moments with Hinawa speaking, the song is called "Memory of Mother".
Claus is the character with the most unused sprites in the game, having around 150. There is an entire set of sprites for young Claus both walking and running in a bathing suit, including one where he dives into the water and resurfaces with a gasp of air from this unused cutscene. There are also several sprites for Claus pushing Lucas, as shown in this video, climbing, cheering, swaying from side to side, yelling, falling backward as if he was hurt, and lying on his back after the fall. This is likely due to the fact that Claus was shown to have a greater role in EarthBound 64 (a trailer of Lucas and Claus in a minecart was prominently shown), but the technological restrictions of the Game Boy Advance made this impossible to implement in Mother 3. However, his younger sprite can still be the party leader in the Debug Room and have his level increased to 99.
There are also multiple unused sprites of Claus when he is older; there appears to be a sprite for him sitting, standing upright, dressed as the Masked Man and walking around, and an in-battle sprite where he still has the cannon on his right arm which can be seen using the enemy modifier code and approaching the enemy from behind. There is a notable set of Masked Man sprites where he appears to explode, a set where he is thrown backward by something, and when he is first being "built", possibly to be used in a cutscene at the end of either Chapter 1 or 3. The entire series of sprites can be seen animated here.
Claus appears in Super Smash Bros. Brawl as a sticker. Attaching this sticker to the bottom of Ness or Lucas's trophies in The Subspace Emissary increases their PK attack by 13. One of Lucas's alternate costumes also uses Claus's clothing and hair colour.
In Super Smash Bros. Ultimate, Claus appears as a Legend class Spirit, having the Neutral Spirit type. For his Spirit Battle, which is also one of the last Spirit Battles in the Adventure Mode alongside Hinawa, Claus is represented by Lucas in his color swap with his colors. After he is KO'd, a reinforcement appears that is Lucas in his color swap resembling the Masked Man. He is metal and his melee weapons have increased power. Claus also appears as a profile icon in the online options.
Masked Man appears as an Ace class Spirit as well, having the Attack Spirit type and increasing sword damage to its user. It can be obtained as a reward for completing the Adventure Mode.
- Claus's name is an anagram of "Lucas."
- When Flint and Alec meet the Magypsies, Aeolia realizes that Flint is his father, noting the resemblance and that they have the same eyes.
- Shigesato Itoi revealed in an interview with Mycom Inc. that Claus and his twin brother Lucas were inspired by two characters of the same name from the novel "The Notebook" (by Agota Kristof), which he described as a novel "about the bonds between twins." The novel is part of a trilogy, which also includes the books "The Proof" and "The Third Lie"—both of which further explore the relationship between Kristof's twin characters.
- The fight background of the final battle with Masked Man is very similar to the fight backgrounds of Ness's Nightmare and Evil Mani Mani.
- In the commercials for EarthBound 64, Claus is depicted with brown hair rather than orange hair.
- While it has been said that Claus was turned into a cyborg by the Pigmask Army, it is not said how much of him was replaced by cybernetics, aside from his right arm still having an arm cannon as seen in an unused sprite.
- Claus' attack sound effect is a Sitar, which can only be heard while fighting Mole Cricket in the prologue. As the Masked Man, he also attacks with this sound effect when using his sword, though only during the first fight.
- In the first fight against the Masked Man, even though lightning is reflected back at him, he takes no damage when the battle begins. However, when fought again as the final boss and lightning is reflected back at him, he takes damage as the battle begins. The reason for this is not explained.
- Ironically, the Pigmask Army made it possible for Claus to fulfill his last sentence to Flint in Chapter 1.
- The Masked Man is said to have no heart. In keeping with this idea, the Masked Man has absolutely no heartbeat file present in the game for either of his battle themes.
- An earlier render of Claus from EarthBound 64 looked like Ness or Ninten.
- Lucas has a palette swap in Super Smash Bros. Brawl, Super Smash Bros. for Wii U and 3DS and Super Smash Bros. Ultimate that resembles Claus.