Laughing Jack’s origins date back to 1800's England, where he was created by a guardian angel as a "not-so imaginary friend" for Isaac Grossman, an extremely lonely child that was often abused by his parents (his mother in particular). Originally a fun-loving and kind clown, Laughing Jack was slowly corrupted into a monster. After accidently killing a cat while playing, Isaac's mother immediately believed it to be her son who did it, since Laughing Jack would. Isaac was sent to boarding school shortly after, forcing Jack to return to the box he was discovered in. As time went by, Laughing Jack's colorful appearance turned monochrome and he became emotionless as a result of his imprisonment. 13 years later, Isaac finally returned as a bitter alcoholic who dismissed Jack as imaginary after the death of his parents. Designed to adapt and develop with Isaac's changing personality, Jack became more and more evil as Isaac became a serial killer who would commit his murders in front of Laughing Jack's prison. Eventually Isaac rediscovered the box Jack was trapped in and accidently released him. Resentful of his former friend and having a newfound love for violence, Jack brutally murdered Isaac and continued spreading his own brand of "fun" to all the other children of the world.
Jack’s clawed arms are capable of stretching, allowing him to pull his victims closer to him. He is also an expert at hiding.
- Teleport - Laughing Jack teleports in black smoke.
- Funny Punch - Laughing Jack winds up his fist and slams it into the ground, creating an explosion. If it's not charged up, the punch just makes the opponent bounce up.
- Tenderizer - Laughing Jack rapidly punches in a certain direction.
- Funny Slam - Laughing Jack stretches out one arm to grab the opponent. If he successfully grabs him/her, he slams him/her several times before the final smash.
- Jack Top - Laughing Jack spins around with his arms out, while moving slightly forward as he spins.
- Jack Buster - Followup to Jack Top, using the momentum from the aforementioned move, Laughing Jack wallops the foe with an uppercut.
- Jumping Jack - Laughing Jack quickly bursts himself up into the air and slams down into the ground, creating a shockwave.
- Throw - Laughing Jack grabs the opponent and jumps over him/her with his arms stretching, followed by throwing him/her.
- Reverse Throw - Grabbing the opponent, Laughing Jack stretches him arms and socks the opponent. He then throws him/her.
- Long Reach - When Laughing Jack's eyes go red, he can change the shape of his arms and stretch them further, making them grow so that he can deal more damage.
- Pop Goes the Weasel - Laughing Jack places a jack-in-the-box under the opponent as Pop Goes the Weasel plays. When the final verse finishes, the jack-in-the-box pops up and impales the opponent.
- Laugh this Off! - Laughing Jack slams the opponent into the ground, then starts beating him/her via winding up his body for continuous momentum before he lilfts him/her up and punches him/her in the chest, ripping out his/her heart and several other organs.
- Laughing Jack plays an accordion.
- A jack-in-the-box is seen and starts playing Pop Goes the Weasel. When the final verse ends, Laughing Jack jumps out and says “Come one, come all! Whether big or small! To see the best clown of them all!! The one, the only, LAUGHING JACK-IN-A-BOX!!!”
- Laughing Jack dances like a monkey.
- Laughing Jack says, "It's been a blast kiddo, but it looks like our time is up." He then jumps back into his box.
- "Come on, it's no fun if you don't watch!"
- "Feeling tired already? Why, we're nearly at the grand finale!"
- After the incident with James, Laughing Jack was contemplating his next victim. But he couldn’t find anyone. To him, something wasn’t right. It just wasn’t fun enough. Then, Jack heard about a god that was gathering people to fight and the winner would get their wish granted. Perhaps now Jack could find a way to add more fun in his life.
Laughing Jack wants to tell Eyeless Jack a joke, but Eyeless Jack says he has no time for jokes. As he tries to leave however, Laughing Jack pulls his mask and snaps it back on his face, annoying Eyeless Jack and prompting him to take Laughing Jack on.
Both are named Jack and are nicknamed as well. They also have supernatural origins but from opposite sides: Eyeless Jack (At least this version) is a possessed human and Laughing Jack was created by an Angel. Both were also formerly friendly but later became murderous monsters: Jack was originally a Straight A student but was possessed by a demon and Laughing Jack was created to be a friend to Isaac Grossman but abuse as well as observing Grossman’s habits turned him into a monster.
Laughing Jack: Hey, Jack!
Eyeless Jack: What?
Laughing Jack: I have a joke for you.
Eyeless Jack: I don’t have time for jokes now.
(Eyeless Jack tries to leave but Laughing Jack pulls back his mask and snaps it back on his face.)
Eyeless Jack: OW!
(Laughing Jack starts laughing manically as Eyeless Jack gets out his scalpel.)
Eyeless Jack: Try laughing after I tear your organs out of your body!
Laughing Jack: You have no sense of humor, do you?
- After defeating Mr. Creepypasta, Laughing Jack was surprised by what he found: A being similar to him named Laughing Jill. Jack and Jill became good friends and together they indulged in Jack’s usual activities. But to Jack, now that he had someone to help him, it just made it all the more fun.
- A lot of moves are borrowed from Super Skrull from Marvel vs. Capcom 3 (ex: Laguh this Off! is a more violent variation of Super Skrull's Death Penalty hyper combo).
- His Pop Goes the Weasel finisher is based on one of Sektor's fatalities.
- SabrinaNightmaren's OC, Laughing Jill, appears in his ending in Arcade Mode.