Chopper, called Batabata (バタバタ) in the Japanese manual, is the gnashing piranha fish that leaps up from under bridges to attack in Green Hill Zone in the 16-bit version of Sonic the Hedgehog, as well as in Bridge Zone on the 8-bit version. They can be easily destroyed by jumping on them as they come up; one should always be wary of them when one crosses a bridge.
A robotic fish resembling a piranha, presumed to be Chopper, Masher, or possibly Jaws, appears in Sonic Adventure as one of the many fish that Big can catch.
Sonic Adventure 2
Chopper made a repeat appearance in the bonus Green Hill stage in Sonic Adventure 2. It is very similar to Sonic 2's Masher. It awards 100 points when destroyed.
Sonic & Sega All-Stars Racing
After a long hiatus, Chopper is brought back to feature in the Seaside Hill tracks (Lost Palace and Ocean Ruin) in Sonic & Sega All-Stars Racing, as an obstacle in water pits. After this game, the badnik appears most regularly.
Sonic the Hedgehog 4
A redesigned Chopper that more closely resembles Sonic 2's Masher in appearance appears in Splash Hill Zone in Sonic the Hedgehog 4. A toy version of this Chopper can be purchased as an Xbox 360 Avatar Prop.
Choppers appear in submerged parts of Aquarium Park in Sonic Colours.
Choppers appear as enemies in Green Hill in Sonic Generations. A giant one is featured chasing Sonic down a system of rails.
Choppers reappear in Sonic Mania, where they once again inhabit the Green Hill Zone. This time around, there are two variations: the first behaves identically to the original version from Sonic the Hedgehog, leaping up from underneath bridges to attack the player; the second functions similar to Sonic 2's Chop Chop, slowly swimming horizontally through the pools of water found throughout the stage, and speeding up while snapping its jaws if the player gets too close.