Morton makes his Paper Mario series debut in Paper Mario: Color Splash. In this game, he has stolen the red Big Paint Star. He is encountered at the top of The
Crimson Tower and acts as the game's first boss. In combat, he uses his magic wand transformed into a large wooden hammer. In the first part of the battle, Morton stays on a pedestal taken into battle by two Shy Guys, that also aid him in battle, and retreats on his shell as Mario attacks. While on the pedestal, Morton can attack by slamming on the ground, creating a shockwave that deals 4 HP of damage and inflicts the Crumpled status effect if not blocked. After the pedestal is blown away by Mario's hammer, Morton directly attacks Mario with the hammer, dealing 8 HP of damage, or by spinning his shell, dealing 12 HP of damage, then, after a while, he calls for two Shy Guys who bring another pedestal in battle and fight with him. Once Morton has received enough damage, he sets his hammer ablaze, drastically increasing its attack power to 48 HP. The fire can be put out using a Fire Extinguisher Thing card, that leaves only the grip of the hammer intact, decreasing its attack power to 1 HP. Upon being defeated, Morton will allude to his Master ordering him to steal the red Big Paint Star, causing Huey to deduce that someone else was indeed searching for the Big Paint Stars. In the Japanese version upon being defeated, Morton instead says 「おかた」, which translates to this gentleman, which was presumably done to avoid giving away that Bowser, or rather, Black Bowser had been behind the theft of the Paint Stars before his formal debut.
Through hacking, it is shown that even with overpowered/powerful cards, the player cannot beat Morton without the fire extinguisher, as his HP will not go down after a certain point.
Unlike in Mario & Luigi: Paper Jam, Morton speaks in a simple, loud, and unintelligent manner similar to Lava Piranha from the first game. He also often does not realize what is happening until he stops for some seconds to think. These traits were later carried over to the Mario & Luigi games starting from Mario & Luigi: Superstar Saga + Bowser's Minions. Furthermore, like other paper characters, he has black eyes instead of gray eyes.