Terrapins are armored Koopas with green shells that appear in Super Mario RPG: Legend of the Seven Stars. In the game, they are the weakest soldiers in the Koopa Troop, even weaker than a Goomba. A similar (and much stronger) enemy is the Terra Cotta. The word "terrapin" is an ambiguous term referring to turtles, which Koopas are quite similar to.
Terrapins fight solo or in groups of two to four and attack their opponents by punching, which does not do much damage. They patrolled the halls of Bowser's Keep in search of intruders, and appear mostly in the very beginning of the game, before Exor crashes into Bowser's Keep. They only had 10 HP and 1 attack power, and 8 defense; this made battling them good training for Mario at that point in the game. Mario also gains no EXP for defeating them.
Terrapins are the precursors to the Koopatrols of the Paper Mario series. However, Terrapins and Koopatrols themselves are very different from each other in stats, although their main purposes are identical in that they are both armor-clad Koopas who guard Bowser's Castle.
Can either be a Bruiser or a Scrapper.
Armored shell - very high crit resistance. Immune to bleeding.
(enemy) Pain Train - causes Pain. Applies Exposed to targets with Pain. Applies Wide-Open to targets with exposed.
(enemy) Tenderized - takes extra damage from slashing attacks.
(enemy) Combo Setup - next unarmed attack against this target does extra damage
(special) Exploits Combos - does extra damage to enemies with Combo Setup
(special) Deadly Crits - does extra damage on critical hits