Chop-Chop is an aquatic-based Badnik created by Dr. Eggman. Modelled on a piranha, this Badnik first appeared in Sonic the Hedgehog 2 and could move through the water faster than its Chopper and Jaws predecessors.
The Chop-Chop is an underwater-based Badnik modelled on a piranha. It has a cylinder-shaped body with a hydrofoil engine on either side of it and a single dorsal and anal fin. Its head is larger than its body and has a mouth filled with razor-sharp fangs.
The Chop-Chop will swim slowly through bodies of water until a target is spotted, at which point it will rapidly gnash its fangs and rocket toward its target at full speed, tearing its prey to shreds with its teeth.
Sonic the Hedgehog 2 (16-bit)
In their first game appearance, Chop-Chops are encountered in the waters of the Aquatic Ruin Zone. They float slowly through the water at first, but once they catch sight of the player they will charge quickly through the water to bite the player. They can only make contact damage when the player is not jumping or rolling and will be destroyed by a single jump or spin attack.
Sonic Pocket Adventure
Chop-Chops make their second appearance in Sonic the Hedgehog Pocket Adventure. These Badniks are seen at Aquatic Relix Zone, which contains similar Badniks and gimmicks. Chop-Chops are seen in underwater sections and have their same attack pattern from Sonic the Hedgehog 2.
Sonic the Hedgehog 4: Episode II
Chop-Chops make their third game appearance in Sonic the Hedgehog 4: Episode II. The Badnik looks similar to the one in Sonic the Hedgehog 2, though it has a smoother appearance and its eyes are open. Despite that, the attack pattern is almost the same, except now it can now turn back after charging and attack from behind the player. It appears in Sylvania Castle Zone and White Park Zone Act 3, being one of the few enemies in the game that appear more than one Zone.
Sonic the Hedgehog Yearbook 1992
A large variation of Chop-Chop has appeared in Sonic the Hedgehog Yearbook 1992' story "Big Trouble". Dr. Robotnik comes upon the idea of building giant-sized Badniks and using them to destroy Sonic and Tails, but his scheme comes undone when he gets involved directly. Sonic and Tails lure Robotnik into giving chase in his Egg-o-Matic, swimming through the water that's being patrolled by the giant Chop-Chop. In the end, Robotnik is lured into the Chop-Chop's path and his Egg-o-Matic crashes into it, destroying it.
Adventures of Sonic the Hedgehog
A small number of Chop-Chops appear in the pilot episode of Adventures of Sonic the Hedgehog. The Chop-Chops, some Mashers and an Octus chase Sonic as he tries to stop Doctor Robotnik's attempts to drain a lake. The Mashers, Chop-Chops and Octus are all defeated when they become entangled in seaweed that whips up behind Sonic as he swims past at high speed.