Snapjaw

Snapjaws are enemies which resemble small crocodiles that attack with gnashing teeth. The appearance of Snapjaws alters in every game they appear in.

Donkey Kong Jr.
Snapjaws first appear in the game Donkey Kong Jr.. Here, they are thrown by Mario at Donkey Kong Jr. in an attempt to defeat the ape. Like Donkey Kong Jr., Snapjaws can climb vines. Though whereas regular blue Snapjaws simply fall off a vine when they reach the end of it, the red variety can continually climb up and down a vine and walk on platforms. In this game, Snapjaws can only be defeated by dropping fruits on top of them. The Snapjaws of this game are quite robotic in appearance.

Donkey Kong (Game Boy)
In Donkey Kong on the Game Boy, Snapjaws appear in Stage 2-4 in the Forest and several other levels after this one. In this game Snapjaws have a more dragon-like appearance. They can be defeated by using a hammer.

Mario vs. Donkey Kong
The next appearance of Snapjaws was in Mario vs. Donkey Kong. Here they were plant-like beings with thorn-like spines covering their body. Along with appearing in various of the game's levels Donkey Kong throws differently-colored Snapjaws as weapons in his and Mario's final battle, similar to what Mario did with them in Donkey Kong Jr. Like in Donkey Kong for the GBA Snapjaws can be defeated in this game using a hammer.

Mario vs. Donkey Kong 2: March of the Minis
Snapjaws appeared in the Mario vs. Donkey Kong 2: March of the Minis level, Jungle Hijinks. Here they looked like green mini toys. They eat vines, and if a Mini Mario touches one, the Mini Mario will be defeated.

Mario vs. Donkey Kong: Minis March Again!
Snapjaws reappear in Mario vs. Donkey Kong: Minis March Again!. They are found only in two boss battles in which they serve as shields for Donkey Kong. They do not fall from their vines.

Yoshi's Island DS
The Snapjaw returned in Yoshi's Island DS under the name Snap Jaw. These crocodiles were much more organic-looking than their mechanical cousins. In this game, Snap Jaws were usually found in levels where vines were abundant, and where Baby DK was the primary baby (such as in World 3). Snap Jaws usually climbed up and down on short vines, apparently clinging to them with their huge jaws. They would sometimes fall from their vines, attempting to knock Baby DK from the Yoshi's back. They are part of the Koopa Troop.

Trivia

 * The appearance of Snapjaws in Donkey Kong Jr., that of large a fanged monster with a chain dragging behind it, is similar to the appearance of another creature encountered in later games of the Mario series, the Chain Chomp.
 * Klaptraps, small crocodilians from variations of the later Donkey Kong games may be based off Snapjaws.
 * A Snapjaw makes a cameo appearance in the Game Boy Camera accessory for the Game Boy handheld system. In the SHOW option a Snapjaw is this options cursor, this seems to make a Snapjaw "quasi-playable".