From the Super Mario Wiki
Green Electro-Koopas are a large variant of the Electro-Koopa species derived from Koopa Troopa. Green Electro-Koopas are one of the three types of Electro-Koopas, quadrupeds with electrical shells. The green Electro-Koopa is found at Pinna Park, specifically Episode 5, The Runaway Ferris Wheel.
A green Electro-Koopa, the source of the problem in The Runaway Ferris Wheel, sleeps on a metal grate behind the Ferris Wheel in Pinna Park. Its electrical discharge makes the ride spin uncontrollably, surprising the visitors at the park. Mario can defeat this Electro-Koopa by flipping the grate beneath it, causing it to fall in the water, and making a Shine Sprite appear atop the flag on the Ferris Wheel. After the Electro-Koopa is defeated, the Ferris Wheel's speed returns to normal.
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