Pachi-Pachi would have been one of the bosses encountered on King Dice's game board. In the finished game, Cuphead and Mugman can roll a die and progress a number of spaces. Depending on the space they land on, King Dice will transport them to a different battle with one of the casino bosses.
In Pachi-Pachi's boss fight, he would travel from side to side, occasionally firing a large vertical laser beam from his head. The player, as Cuphead or Mugman, would have to avoid the laser as well as pachinko balls that would fall from the top of the screen and tilt the platforms they were standing on. If Pachi-Pachi managed to kill the player, it would gloat in rhyme. However, if the player beats the boss and continues the game, Pachi-Pachi would have painfully fallen apart before being left behind.
Though Pachi-Pachi was one of the most complete unused bosses in the game, he was ultimately scrapped for unknown reasons, though the most common explanations were to keep the level from being too long or too unfair, and because the Japanese-invented pachinko machines did not come to the Americas until 1970s, roughly forty years after the time period the game is set in.