The Chopper closely resembles a piranha; it has an ovoid body with pelvic and dorsal fins and a fishtail and its mouth is filled with razor-sharp teeth. In most of their appearances, Choppers will leap out of the water and over bridges and walkways, constantly snapping their jaws in order to bite anyone attempting to pass by.
Sonic the Hedgehog (1991)
Choppers appear in both the 16-bit and 8-bit versions of Sonic the Hedgehog, appearing in the Green Hill Zone in the 16-bit version and in Green Hill, Bridge and Jungle Zones in the 8-bit version. In both, their sole method of attack is to constantly leap up and down from beneath bridges while constantly snapping their jaws. They actually cannot hurt Sonic unless he runs directly into them and are easily defeated by a spin jump or spin attack.
Sonic the Hedgehog 2 (8-bit)
An unnamed Badnik that closely resembles the Chopper appears in the Crystal Egg Zone. Unlike in Sonic 1, these foes do not jump up and down and do not bother the player at all, instead just slowly floating through bodies of water. They can be easily destroyed with any attack.
Sonic Adventure 2
After collecting all 180 emblems in Sonic Adventure 2, the player unlocks a hidden stage: a 3D recreation of Sonic 1's Green Hill Zone. Choppers and Buzz Bombers are the only enemies to appear in this stage. Unlike its previous 2D appearance, the Chopper does not just jump up and down in a straight line and will leap in an arc over bridges. It is still not a very capable opponent and can be easily defeated by any of Sonic's attacks.
Sonic the Hedgehog 4: Episode I
Choppers return after a long absence in Sonic the Hedgehog 4. Their appearance has been slightly modified and now look more like the Masher Badniks from Sonic the Hedgehog 2 (although arguably the Chopper and Masher are the same model of Badnik as they both look and act similarly to each other). Aside from having yellow underbellies, the Choppers have not changed much at all and still attack in the same jumping fashion as before.
Choppers appear in both the Nintendo DS and Wii version of Sonic Colours, where they are encountered in the underwater sections of Aquarium Park. Choppers in these games are colored pink, grey and yellow, though the concept arts relates this to Jaws. Throughout the six Acts of this Area, schools of normal-sized Choppers and very large Choppers infest the many waters that Sonic travels through.
In the Wii version, eight Choppers also appear in the underwater tunnel section in Asteroid Coaster Act 6 and in several underwater sections in Game Land which are related to Aquarium Park and Asteroid Coaster.
In both the console/PC and Nintendo 3DS versions of Sonic Generations, Choppers can be found in Green Hill and Seaside Hill. They have the same color scheme and uses the relatively same attack pattern from the original Sonic the Hedgehog, though they are not powered by animals. In the second acts of the stages they appear in, the Choppers jump in arches over their bridges.
The console/PC version of the game also features a giant-sized Chopper that destroys the Grind Rails in a cave in an attempt to catch and defeat Modern Sonic. This Mega Chopper later reappears in Seaside Hill; if the player attempts to abuse the hydroplaning effects of the Boost and leave the Stage's boundaries, the Mega Chopper eats Sonic.
Sonic Lost World
Like all other Badniks in this game, the Choppers have returned to a more simplistic, cartoonish design. Appearing in multiple stages, they will jump out of bodies of water (or oil, in some cases) and arc over footpaths trying to bite Sonic. They move slower than before and are easier to hit. They can be destroyed with either a spin-jump or focused homing attack.
Choppers appear in the Green Hill Zone, retaining the same appearance and behaviour from Sonic 1. As well as jumping up from beneath bridges, however, some Choppers in Act 2 can be seen lurking in pools of water. If they spot the player, they will start gnashing their teeth and will swim quickly toward the player.
While nearly all of Eggman's Badniks in Sonic Forces are older models that have been redesigned, the Chopper seems to have been altered the least in comparison to the other Badniks in the game. Its colour has been changed to magenta while its eyes are yellow and lack pupils. Its behaviour is the same as it was in its first appearance; it appears in Classic Sonic's Green Hill stage and jumps up and down from below wooden bridges attempting to bite Sonic when he crosses.
Sonic the Comic
In the Sonic the Comic series published by Fleetway Editions, the Choppers are a part of Dr. Robotnik's Badnik army which patrol the waters of the Green Hill Zone. Depending on the artist, the Chomper's design would differ between issues. They have also appeared on two covers and two pin-ups during the comic's run.
Adventures of Sonic the Hedgehog
In the Adventures of Sonic the Hedgehog animated series, the Choppers are Badniks used by Dr. Robotnik. They made a brief appearance in the episode "The Last Resort" where Scratch and Grounder released three Choppers on Sonic while he was water skiing. However, they ended up being used by Sonic to water ski.