Their personalities are shrouded in mystery, as they have never had a single line in any of their games, including the one RPG they appeared in. Only the TV show, The Adventures of Super Mario Bros. 3, which changes their names, gives insight into this.
Larry is the youngest and Ludwig is the oldest. It is presumed that their age, from youngest to oldest, is the order they are fought in Super Mario Bros. 3.
The Koopalings made their first appearance in Super Mario Bros. 3. As a means of distracting Mario, each of them invaded a different land and transformed the king of each land into an animal or enemy. Mario and Luigi set out to stop them and take their magic wands to change the kings back. They fought them aboard airships, and defeated them in this order: Larry, Morton, Wendy, Iggy, Roy, Lemmy, and Ludwig. After being defeated, the Koopaling would retreat. They can be defeated with a few fireballs or by jumping on them three times.
Mario and Luigi fought a Koopaling at the end of each level. Larry was fought at Bowser's level before his castle. In order, Mario and Luigi defeated Iggy, Morton, Lemmy, Ludwig, Roy, Wendy, and Larry. Upon defeat, Iggy, Lemmy, Wendy, and Larry fell into the lava, while Morton, Ludwig, and Roy spiraled into the distance (or simply got smaller) and exploded in a puff of smoke.
The Koopalings returned in this game, and were sent by Bowletta, who gained all of Bowser's minions and possessions when she possessed him, to fight Mario and Luigi, but they defeated them in the same order as Super Mario World: Iggy, Morton, Lemmy, Ludwig, Roy, Wendy, and Larry. Roy, Wendy, and Larry use Time Bob-ombs that last eight turns. Once defeated, the Koopaling would disappear in the usual enemy death scene, leaving only a portal leading to a previous room.
For the first time, the Koopalings appeared alongside their brother Bowser Jr., as well as Kamek. They are also given voices in this game. Together, the Koopalings and Bowser Jr. hid in a cake and kidnapped Princess Peach for Bowser.
A Koopaling would be fought twice in each stage: First in a tower, and then in a castle. Each castle battle, Kamek would modify with magic. In order, Mario, Luigi, and two Toads defeated Larry, Roy, Lemmy, Wendy, Iggy, Morton, and Ludwig. All of them fell over the edge upon their second defeat, but survived and, alongside Bowser Jr., helped Bowser back up after his defeat, but the castle fell on top of all of them.
- The Koopalings were intended to appear in Super Princess Peach, with their sprites being created, but they decided against it.
- Angry Video Game Nerd, while reviewing Super Mario Bros. 3 and noticing its references to hell, suggests that the Koopalings represent the Seven Deadly Sins.
- Their hair and shell color often change throughout the games, with Larry and Iggy swapping shell color.
- In Super Mario Bros. 3, the Koopalings are in airships, while in New Super Mario Bros., Bowser Jr. is in towers. In New Super Mario Bros. Wii, this is reversed.
- The order they are fought in Super Mario World and Mario & Luigi: Superstar Saga is the same. The battles with Roy, Wendy, and Larry are similar but slightly different than those of Morton, Lemmy, and Larry, respectively, in Super Mario World, and a bit more challenging, while in Superstar Saga the battles are similar but, in addition to new attacks, Roy, Wendy, and Larry are the only Koopalings with Time Bob-ombs in their battles.