Snapjaw

Snapjaws are enemies that resemble a cross between an alligator and a living bear trap. They attack with gnashing teeth and are able to travel along vines.

Donkey Kong Jr.
Snapjaws first appear in the game Donkey Kong Jr. Here, they are used by Mario in an attempt to defeat Donkey Kong Jr. Like the ape, Snapjaws can climb vines. Whereas blue Snapjaws simply fall off a vine when they reach the end of it, the red variety thrown by Mario can continually climb up and down vines and move on platforms. Snapjaws can only be defeated by dropping fruit on top of them. In this game, they appear as fanged monsters with a chain behind them, similar to Chain Chomps.

Donkey Kong (Game Boy)
In Donkey Kong for the Game Boy, Snapjaws appear in Stage 2-4 in the Forest and three stages of the Jungle. They act much as they do in their previous appearance, and Snapjaws thrown by Donkey Kong act like the blue ones of Donkey Kong Jr.; however, as color is not used to differentiate between enemy types, these Snapjaws have spiked bodies and shorter snouts. Snapjaws can be defeated with fruit or a hammer.

Captain N: The Game Master
Snapjaws appear in the episode titled "Queen of the Apes" of Captain N: The Game Master. Like many entities in the series, they are very off-model, being depicted as piranhas with large underbites (incidentally similar to the creature of the same name from Donkey Kong Country 2: Diddy's Kong Quest).

Mario vs. Donkey Kong
The next appearance of Snapjaws is in Mario vs. Donkey Kong. They show up in Donkey Kong Jungle, and have spikes instead of chains. They act similarly to normal red Snapjaws, but move at a less rapid speed when going down a vine, and can change direction in the middle of a vine. The ones that appear in the fifth stage have a red and green coloration, whereas Donkey Kong tosses Snapjaws with a blue and purple palette in the DK stage. These Snapjaws do not fall off their vine; rather, they will climb up a vine approximately twice, at which point they will vanish. Like in the Game Boy Donkey Kong, Snapjaws can be defeated with fruit or a hammer.

Mario vs. Donkey Kong 2: March of the Minis
Snapjaws reappear in the Mario vs. Donkey Kong 2: March of the Minis floor Jungle Hijinks, having a slightly updated appearance. During levels, they eat leafy vines as they move through them, and if a Mini Mario touches one, the Mini Mario will be defeated. During the boss battle against Donkey Kong, three of them repeatedly travel down and up ropes, and fruit can once again defeat them.

Mario vs. Donkey Kong: Minis March Again!
Snapjaws reappear in the Mario vs. Donkey Kong: Minis March Again! floor Jungle Rumble. They serve a similar capacity in the boss battle against Donkey Kong, except they spawn from the top of the ropes over time.

Trivia

 * Klaptraps, small alligators introduced in Donkey Kong Country, may be based off Snapjaws.
 * A Snapjaw makes a cameo appearance in the Game Boy Camera accessory for the Game Boy handheld system, as the SHOW option's cursor.