Sonic 4 Website info
A Piranha inspired robot which was last seen in "Aquatic Ruin Zone" in "Sonic 2". It lurks underwater hunting for its next victim. Once they spot Sonic and his friends, nothing will stop their rapid approach and attempt to crush them with its powerful jaw.
Sonic the Hedgehog 2
Chop-Chop drift aimlessly in the waters of the Aquatic Ruin Zone. Once they spot Sonic or Tails they jet off at high speeds and charge in the players direction with their jaws mashing. These robots can also catch the player unawares by charging backwards too. With water physics slowing down movement as it is, their fairly fast charge can be hard to avoid, it's best to avoid the waters altogether.
Sonic the Hedgehog 4: Episode II
Chop-Chop also appears in Sonic 4: Episode II. It looks similar to the one in Sonic 2, though it has a smoother appearance and its eyes are open. It appears in Sylvania Castle. and Act 3 of White Park.
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 that 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.
This footage is reused in the episode "Untouchable Sonic", on a TV being watched by Scratch and Grounder.