Mildes first appeared in Super Mario World 2: Yoshi's Island. Yoshi encountered a large amount of these goons on his quest to rescue Baby Luigi from Bowser. Often found in groups, the Mildes walked in a straight line, dropping down when they reached a ledge, and turned in the opposite direction when they were opposed by a wall. A Milde could be simply stomped on to defeat, causing sparks of electricity to travel across the ground and bump into other enemies.. They were also able to be made into Eggs, Yoshi's trademark ammunition. Due to their large numbers, they were a good source of eggs for the dinosaur.
In World Four of the game, Yoshi came across a large fortress, called Marching Milde's Fort. Four keys were required to open the inner sanctum. Once the keys were collected and the door became ajar for Yoshi to enter, the world's miniboss, Marching Milde, revealed herself. Marching Milde was very large, but Yoshi ground-pounded her down to size. Every time she was ground-pounded, she would become two smaller Mildes, until she was no more. The Large Mildes encountered in this battle later appear as normal (albeit rare) enemies in stages such as Hookbill the Koopa's Fort.
Mildes return for the first time in years in Lets-a-go, Mario. They act exactly as they did in Super Mario World 2: Yoshi's Island. However, they have a new sub-species in the game, the Ice Milde. Ice Mildes act the same until they are squished. When they are stomped, they freeze all nearby enemies.
- Mildes very much resemble the famous Nintendo character Kirby.
- Their name is possibly a corruption of the word "mild," referring to their carefree nature.
- However, it is much more likely to be a reference to the word "mildew," which Mildes resemble.