Shellcreepers are green-shelled turtles that first appeared in the Mario Bros. arcade game for the NES. 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 the Wii U version of Super Smash Bros. for Nintendo 3DS/Wii U state that the Koopas apparently evolved from Shellcreepers; however, the Japanese text specifies Koopa Troopas.
The Shellcreeper is the first enemy to appear in Mario Bros. They walk out of the Warp Pipes at the top of the screen and walk towards the pipes at the bottom of the screen. The player must hit it from below to flip it over and run into it to defeat it. If the player does not run into it, the Shellcreeper jumps out of its shell (revealing that it wears a white shirt and shorts), flips its shell over, changes color from green to purple and continues moving faster than before. If it flips its shell again, it will turn red, its fastest state. If a Shellcreeper is the last target for the phase, it will automatically turn red. Unlike the similar Koopa Troopa, jumping on Shellcreeper will cause Mario or Luigi to lose a life. Also, Shellcreepers can attack by biting Mario or Luigi with their teeth.
Following the Mario Bros.-style battle mode in Super Mario Bros. 3, Shellcreepers have been replaced by Spinies in all subsequent versions, so they would not be mistaken for Koopa Troopas, which are safe to jump on. Despite this, a lone Shellcreeper still makes a cameo alongside a Sidestepper and Fighter Fly on the title screen of the Game Boy Advance remakes of Mario Bros.
Mario Bros. Special
In Hudson Soft's 1984 sequel of sorts to Mario Bros., Mario Bros. Special, Shellcreepers make a return appearance as enemies, though this time they can't be stunned by hitting them from below; instead, they can be stunned by jumping on a trampoline that they're on (second stage), jumping on a conveyor belt that they're on (third stage), or killed instantly by jumping over or next to them and hitting a platform, though they will often respawn if killed this way.
Punch Ball Mario Bros.
Shellcreepers appear as an enemy yet again in Hudson Soft's semi sequel to Mario Bros., Punch Ball Mario Bros.. The game is much closer to the Mario Bros., and thus Shellcreepers play a much more similar role as they did in that game. The only differences are that they can't be stunned from below and are instead stunned by Punch Balls, and that they do not change color if they get back up after being stunned.
Mario Power Tennis/New Play Control! Mario Power Tennis
Shellcreepers, along with the other Mario Bros. enemies, appear in the background of the Mario Classic Court in Mario Power Tennis, where they use their NES sprites. The game's data includes an unused 3D depiction of a Shellcreeper, showing it as a small, quadrupedal Koopa Troopa with clawed flat feet.
Super Smash Bros. series
In Super Smash Bros. Brawl and Super Smash Bros. Ultimate, Shellcreepers appear on the Mario Bros. stage. They walk out from the pipes at the top of the stage. If knocked over by hitting them from below or from an attack, they can be picked up and thrown at opponents, making them fly sideways off the screen. The Shellcreepers also have their own trophy in Super Smash Bros. Brawl and Super Smash Bros. for Wii U.
Super Mario 3D World
Shellcreepers appear in Luigi Bros., an additional game featured in Super Mario 3D World. Like the other enemies in Luigi Bros., Shellcreepers behave in the same way as Mario Bros., which this game is based on.
Shellcreepers appear in NES Remix in the challenges and remixes based on Mario Bros.
Super Mario Maker
In Super Mario Maker, one of the unlockable playable costumes looks like the Shellcreeper's sprite in Kaettekita Mario Bros. It can be unlocked at random after clearing the 100 Mario Challenge on Expert setting or harder. If the player holds Padup on the GamePad while wearing the costume, the Shellcreeper makes a grimace. While the player runs as the Shellcreeper, its shell turns red.
|Mario Bros. Special||Enemy||1984||PC-8801, PC-6001mkII/PC-6601, PC-9801, FM-7, Sharp X1, Sharp MZ-1500, Sharp MZ-2200, Hitachi S1|
|Punch Ball Mario Bros.||Enemy||1984||PC-8801, PC-6001mkII/PC-6601, FM-7, Sharp X1, Sharp MZ-1500|
|Kaettekita Mario Bros.||Enemy||1988||Family Computer Disk System|
|Mario & Luigi: Superstar Saga||Cameo on the Mario Bros. title screen. Also in the Super Mario Advance ports.||2003||Game Boy Advance|
|Mario Power Tennis||Cameo as enemy on Mario Classic Court||2004||Nintendo GameCube|
|Famicom Mini: Mario Bros.||Enemy||2004||Game Boy Advance|
|Super Smash Bros. Brawl||Cameo as enemy found on the Mario Bros. stage||2008||Wii|
|New Play Control! Mario Power Tennis||Cameo as enemy on Mario Classic Court||2009||Wii|
|Super Mario 3D World||Enemy in Luigi Bros.||2013||Wii U|
|NES Remix||Enemy/objective in Mario Bros. challenges and remixes.||2013||Wii U|
|Super Smash Bros. for Wii U||Cameo as a trophy.||2014||Wii U|
|Super Mario Maker||Unlockable playable character.||2015||Wii U|
|Super Smash Bros. Ultimate||Enemy||2018||Nintendo Switch|