Crab

Crabs are decapod crustaceans of the infraorder Brachyura, which are generally covered with a thick exoskeleton and come armed with a pair of pincers. They are delicious. In the Crash universe, they also make a few appearances as generic enemies.

Crash Bandicoot
Crabs are the first enemies encountered in this game - and, by extension, the entire series. They appear mainly on N. Sanity Beach. They do not directly attack Crash, instead simply walking from side to side while blindly snapping their pincers. They easily fall to a jump or spin attack, coincidentally tactics that work effectively on real-world crabs as well.

Crash Bandicoot 2: Cortex Strikes Back
A crab makes a cameo appearance in the less-than-100% completion ending, passing by as Coco wonders what happened to Doctor Neo Cortex and his Cortex Vortex. This crab is sadly unable to answer her questions, though it is possible that it does know what became of them, but simply does not answer, as revenge for the deaths of his family in the first game.

Crash Twinsanity
Crabs reappear as generic enemies. They appear on N. Sanity Beach and Jungle Bungle - unusual, as real-world crabs typically do not live in jungles. Their appearance seems to be a deliberate throwback to the first game in the series. However, these crabs wear shells, implying that they are hermit crabs and, therefore, not the same crabs that Crash Bandicoot killed in Crash Bandicoot.

Trivia

 * The appearance of crabs as enemies in the Crash games appears to be a reference to the many famous crab enemies from Nintendo's rival Mario series, including Sidesteppers from Mario Bros. and Clawglip from the true Super Mario Bros. 2. Many fans suspect that by making crab enemies - a notorious staple of the Mario games - extremely weak in this game, Naughty Dog seems to be mocking Nintendo, as revenge for not being allowed to develop this game for the N64. Out of embarassment, Nintendo would not include a polygonal crab-based enemy in one of their games until Super Mario Galaxy, 12 years later.