Morton Koopa Jr.

Morton Koopa Jr. is presumably the second youngest of the seven Koopalings, the seven kids of Bowser who appear in several Mario games. He also appears in two Mario cartoons where he is known as Big Mouth Koopa. He also appears in a Japan exclusive Mario anime where he goes by his real name.

Super Mario Bros. 3
Morton is the second Koopaling to be fought. He is encountered in an airship at Desert Land. His fighting style is similar to that of his younger brother Larry. Once defeated, he runs off, leaving behind the wand he used to transform the king of Desert Land.

Super Mario World
Again, Morton is the second Koopaling to be fought. He is fought in a room where the walls are slowly closing in, and often comes onto the ceiling. To defeat him, as in Super Mario Bros. 3, Mario must jump on him three times. Once defeated, he spiraled into the distance and exploded in a cloud of smoke.

Mario & Luigi: Superstar Saga
Morton returned in Mario & Luigi: Superstar Saga, working for Bowlettain Bowser's castle. As usual, he is the second Koopaling to be fought. Once defeated, he apparently dies like the others, and vanishes.

Super Princess Peach
Although not actually seen in the game it was revealed that Morton along with his other siblings(excluding Bowser Jr.) were to make an appearence in this game but were taken out for no apparent reason. Every one of the Koopalings had their own complete sprite sheet.

New Super Mario Bros. Wii
Morton reappeared in New Super Mario Bros. Wii. This time, he is the sixth Koopaling to be fought, and is not the boss of a desert land, but a mountain land. Like the others, he is fought twice per level. The second time he is fought, Kamek casts a spell on the floor so that whenever Morton pounds the ground, the two parts of the ground on either side of him will go up and touch the ceiling, crushing anyone who is standing on it at the time. Once defeated, Morton fell off the screen, but survived, as he was seen alongside Bowser, Bowser Jr., and the other Koopalings, before Bowser's castle fell on top of them and crushed them.

Mario Kart 8
Morton and all of the other Koopalings made their first appearance as playable characters in ''Mario Kart 8. ''Morton and Roy were the only two Koopalings to be in the large class.

Super Smash Bros for Wii U and Super Smash Bros for Nintendo 3DS
Morton Koopa Jr. has been confirmed to be an alternate costume for Bowser Jr. in the video games; Super Smash Bros. for Wii U and Super Smash Bros. for Nintendo 3DS.

Physical appearance
Morton is the only of the seven Koopalings who has a black skin instead of the yellow one. His head is white with a black star on his left eye. His snout is light pink like his brothers, his shell is black and his stomach and feet a are padded.

In Super Mario World, he has a Green sheel and a Green Head and Orange Skin

Trivia

 * Morton's name is derived from Morton Downey Jr.