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Pesky Clown (嫌なピエロ, Iya-na Piero) is a Mysterious Being. He was killed by Sweet Mask.


Pesky Clown is a stereotypical clown with red face paint over his eyes, nose and mouth with white face paint over the rest of his face. His teeth are razor sharp. His sleeves and collar puff out widely. His shirt is patterned in many bow ties with a polka dot pattern on the arms. The monster's pants are tucked into his spiky pointed boots. Pesky Clown carries balloons shaped like animal heads and a large mallet. He increases in size and becomes more monstrous as he gets stronger. His last form before Sweet Mask defeated him possessed four arms with an massive mouth and eyes located on the torso. This last form towered over Sweet Mask in the hero's transformed state.


Pesky Clown enjoys attention and is sadistic. However once it was clear he had no chance against Sweet Mask in his transformed state, he begged for mercy, indicating a cowardly side to his personality.


Neo Heroes Saga[]

Supreme Hero Arc[]

Pesky Clown's death at the hands of Sweet Mask.

Pesky Clown appears at the I-City Grand Amusement Park and terrorizes the parkgoers. He kills several guards who try to stop him before Sweet Mask confronts him. At first, Sweet Mask overwhelms him, and he loses all of his balloons. However the spectators gathered around the fight give him attention, which significantly increases his power. He thrashes Sweet Mask around and punches him into the Ferris wheel, forcing the hero to release his true form.

After Sweet Mask's release, Pesky Clown is overwhelmed by Sweet Mask as he breaks his left leg and right arm and mercilessly releases multiple barrages of punches on his face and torso. However, the worldwide attention that Sweet Mask's appearance brings to the fight gives Pesky Clown more and more power, transforming him into an even bigger monster with four arms and a second face with a huge mouth on his stomach.

In this new form, Pesky Clown pummels Sweet Mask and overpowers him easily. As he tries to devour Sweet Mask with the newly-gained mouth on his stomach, Sweet Mask escapes from his mouth, tearing the skin at edges as he does so. Realizing he has lost, Pesky Clown yields and begs Sweet Mask to show him mercy only to be punched into a bloody mess on the ground by Sweet Mask.

Abilities and Powers[]

Although Pesky Clown is initially classified as a Wolf-level threat, he transforms several times during his fight with Sweet Mask, eventually gaining enough strength to even make the powerful hero struggle. Sweet Mask estimated his highest threat level to be Dragon. He is, notably, the only monster thus far to force Sweet Mask to use his monster form.

Physical Abilities[]

Immense Strength: Pesky Clown boasts very impressive strength. Although initially unable to hold his own against Sweet Mask, his strength eventually grows to the point that he is able to easily pummel Sweet Mask, and the hero proclaims that he's too strong to defeat while in his human form. He also punched Sweet Mask hard enough to demolish a Ferris wheel.

Immense Speed and Reflexes: Pesky Clown is exceptionally fast. Initially unable to react to any of Sweet Mask's attacks, as he grows, he manages to block one of the hero's attacks with his hammer and eventually catch Sweet Mask by surprise. He becomes capable of trading blows with Sweet Mask.

Immense Durability: Pesky Clown is extremely resilient already being bullet proof after his recent change. Initially, his head and neck had been demolished by singular nonchalant strikes to his frame. As he grows, his durability increases to the point of being able to withstand Sweet Mask's blows with no apparent damage.

Pesky Clown's Monster Form after accumulating worldwide attention.

Transformation: Pesky Clown has the ability to transform in order to increase his power. He draws power from the attention he receives; the more spectators there are, the stronger he grows. This allows him to grow to the point that he's able to overpower Sweet Mask, the top-ranking A-Class hero with S-Class abilities, and cause the hero to proclaim him too strong to defeat while in his human form.

Accelerated Development: The longer he fights against a more capable opponent than himself, the more Pesky Clown adjusts and evolves in order to match them. Sweet Mask calls such a monster a "Rapid Growing" type.

Fighting Style[]

Hand-To-Hand Combatant: Pesky Clown lacks a refined fighting style, but he was skilled enough to evenly exchange blows with Sweet Mask and eventually overpower him.

Miscellaneous Abilities[]

Damage Shift: By unknown means, Pesky Clown has the ability to transfer damage he takes to his balloons. Once a balloon reaches its damage threshold, it pops.


  • Mallet: Pesky Clown has a large mallet that he uses to attack and block with. He uses it to great effect.
  • Balloons: Pesky Clown had three balloons that allowed him to sustain damage without dying. When a balloon's damage threshold was reached, it popped, and he restored his original state.[5] All three balloons were popped by Sweet Mask.


  • Pesky Clown is the only monster to have four disaster levels, going from Wolf (his official disaster level) to powering up to Tiger, then Demon and eventually Dragon. It is unknown if he could have increased his disaster level further from there.
  • He is the first Dragon-level monster killed by an A-Class hero other than Saitama in the story.


  1. One-Punch Man Webcomic; Chapter 121, page 22
  2. One-Punch Man Webcomic; Chapter 121, page 15
  3. One-Punch Man Webcomic; Chapter 121, page 6
  4. One-Punch Man Webcomic; Chapter 121, page 14
  5. One-Punch Man Webcomic; Chapter 121, page 3, page 12


Mysterious Beings
Dragon (or higher) Boros Orochi *
Demon 170,000-Year-Old Cicada Larva 170,000-Year-Old Cicada Adult Armored GorillaAwakened Cockroach Baquma Beast King Bug God Building Booper Deep Sea King Demonic Fan Devil Long Hair *Do-S *Face Ripper Fist Fight Djinn Free Hugger G4 G5 Game-Berus Giant Crow Grizzly Nyah Hundred-Eyes Octopus Jumping Spider Mosquito Girl *Rafflesidon Rhino Wrestler Royal Ripper Scaledon Senior Centipede Showerhead Sky King Subterranean King Super Mouse The Great Food Tub The Three Crows Unihorn Vampire (Pureblood) 
Wolf Himawari Hotdog Messenger of the Seafolk Piggy Bancon Tongue Stretcher
Less than Wolf
Unknown Alien Seer *Ancient King Autumn Phantom Red Golden-ringed Dragonfly *Benpatsu *Choze Dark Matter Gunner Eagle Enamel Evil Eggs Evil Eye Eyesight Falcon Fish of DarknessGale Gigakigan Goddess Glasses Gyoffrey Hamukichi *Haragiri Hawk Hellfire Junior Centipede *Kite ManakoPlatinum SpermRosie Raptora *RepteraSuppon Sword Devil Executioner Venus Mantrap Volten *