The Koopa Kids (called Mini Bowsers in Europe, and originally known as Baby Bowsers in all non-Japanese versions of the first three Mario Party games) are minions of Bowser who only appear in the Mario Party series. The Koopa Kids resemble miniature versions of Bowser (and are therefore very similar in appearance to Bowser Jr. and Baby Bowser). A Koopa Kid also appears as a playable character in Mario Party 5 and Mario Party 6.
In the earlier games in the series, there appears to be a large number of Koopa Kids, as shown by minigames such as Baby Bowser Bonkers in Mario Party 3, with the Koopa Kids being capable of splitting themselves. Indeed, Mario Party 4 specifically refers to the Koopa Kid who appears on Bowser Spaces as "one of the Koopa Kids". However, starting in Mario Party 5, there seems to be only a single Koopa Kid of the regular coloration, likely due to his new playable status (though multiple Koopa Kids do appear in Super Duel Mode in the aforementioned game). The other Koopa Kids in the game are divided into color: Green K. Kid, Red K. Kid, and Blue K. Kid (Green M. Bowser, Red M. Bowser and Blue M. Bowser in British English). However, more than one standard Koopa Kid can appear at once in Mario Party 7 (where Koopa Kid is non-playable again) in Pyramid Park.
The Koopa Kids have been removed from the Mario Party series starting in Mario Party 8, in favor of Bowser Jr., who appears in Mario Party DS and onwards. This is further proven by Bowser Jr. outright replacing Koopa Kid in various minigame remakes in Mario Party: The Top 100 and Mario Party Superstars.
Mortal Kombat: Shinnok's Uprising[]
It was mentioned by Aiko to Kung Lao that when she was younger, the Kombatants had allies from other realms, even though they were temporary due to the anomalies caused by the rips in Earthrealm's dimensional fabric. One of those incidences was when Bowser and the Koopalings were in peril by Shao Kahn and his extermination squads. Being that the Koopa King was overmatched, he allied with the heroes providing them with their assistance. Once Kahn regained his lost strength after the failed insurrection of Outworld, the younger Aiko was sent home and Bowser and his Koopalings were never seen again.