Shellcreepers are green-shelled turtles that first appeared in the Mario Bros. arcade game. They are the first turtle enemies to appear in a Mario game, making them the conceptual ancestors of the Koopa Troopas, which appeared two years later in Super Mario Bros. It is also shown that Shellcreepers wear undershirts and shorts when outside of their shells; Koopa Troopas first appeared out of their shells in Super Mario World wearing a shirt, and in Super Mario World 2: Yoshi's Island wearing shorts. The trophy descriptions in Super Smash Bros. for Wii U state that the Koopas apparently evolved from Shellcreepers; however, the Japanese text specifies Koopa Troopas.
Given they are the first turtle enemies to make an appearance in a Mario game, they are essentially the precursor to the Koopa Troopa.
Shellcreepers are also known to wear undershirts and shorts when outside of their shells. It is stated from the trophy descriptions in Super Smash Bros. for Wii U that the Koopas evolved from Shellcreepers.
The Shellcreeper was given many different names in different languages.
- Its Japanese name is カメさん Kame-san (Turtle-san) シェルクリーパー Sherukurīpā (Shellcreeper).
- Its Spanish name is Tortuga (Turtle).
- Its French name is Carapeur, which is a pun on carapace (the upper shell of turtles) and peur (fear).
- Its German name is Schildkröte (Turtle).
- Its Italian name is Tartaruga (Turtle).
- Its Russian name is Черепашкин (Cherepashkin), which comes from черепаха , which means cherepakha, turtle.
- Its Korean name is 거북님 (Geobuk-Nim), which is a translation of its Japanese name.
Shellcreepers are the first enemies players encounter in the game. They emerge from the Warp Pipes at the top of the screen and will make their way towards the bottom. The player must use the traditional method of bumping them from underneath their platforms to incapacitate them. When knocked over, the player can run up to them and automatically kick them off-screen. If the player does not do this within a limited amount of time, the Shellcreepers flip back over, creeping back out of their shells and turning yellow, moving at a faster speed. If this is repeated again, they turn red and move at their fastest speed. This automatically happens to the last remaining Shellcreeper in each phase. Jumping on these foes results in the player losing a life. They also attack by biting Mario or Luigi, which also results in a life loss.
Shellcreepers have been replaced with Spinies in versions following the battle mode of Super Mario Bros. 3, as to avoid confusion between them and the Koopa Troopas. However, a single Shellcreeper is still featured on the title screen of each Game Boy Advance remake.
Shellcreepers return as enemies in Super Mario Bros. Special, a follow-up game developed by Hudson Soft. Unlike the previous game, this game has a new method of attacking these foes. Instead of striking them from below, they can be stunned by jumping on a trampoline they are on (second stage), jumping on a conveyor belt (third stage), or can be instantly defeated by leaping over or beside them and hitting a platform. However, they will often respawn if this method is used.
Shellcreepers return once again as enemies in Punch Ball Mario Bros., which is a semi-sequel to Mario Bros.. They have a much more similar role as they did before. However, Punch Balls are the new method of attack against these foes, and they do not change colors upon regaining consciousness.
Shellcreepers appear in the background of the Mario Classic Court in Mario Power Tennis, along with other enemies from Mario Bros., still retaining their NES sprites. The game's data contains an unused 3D depiction of a Shellcreeper, which shows it as a small, quadrupedal Koopa Troopa flat, clawed feet.
In Super Smash Bros. Brawl and Super Smash Bros. Ultimate, Shellcreepers are featured on the Mario Bros. stage. They emerge from the pipes at the top of the stage. If the player incapacitates them with a hit beneath or an attack, they can pick them up and throw them at other opponents, making them fly offscreen sideways. Shellcreepers also have their own trophy in Smash Bros. Brawl and its Wii U remake.
A game within Super Mario 3D World, Luigi Bros., marks yet another appearance of Shellcreepers. This game is based on Mario Bros. Like other enemies in Luigi Bros., they retain the same behavior as in Mario Bros.
Shellcreepers are featured in NES Remix, appearing in challenges and remixes based on Mario Bros.
Although, Shellcreepers do not officially appear in Super Mario Maker, there is an unlockable costume that resembles the sprite of a Shellcreeper in Kaettekita Mario Bros. It is unlocked at random after the player clears the 100 Mario Challenge on Expert difficulty or higher. Holding the 'Up' button on the GamePad while in the costume will cause the Shellcreeper to make a grimace. Its shell will turn red when the player runs in the costume.