The Flasher is a Badnik that is modelled after a firefly. It has a red-coloured insectoid head with a pair of thin antennae and its body consists of a black shell with a large bulb beneath it. The Flasher's bulb is capable of generating a deadly field of electricity, shocking anyone that comes near it.
Sonic the Hedgehog 2
To date, Sonic the Hedgehog 2 is the Flasher's only game appearance. Encountered in the Mystic Cave Zone, these robotic fireflies hover around in the air. When they stop, they generate an electrical shield and cannot be touched without the player taking damage. They can only be attacked while moving as their electric shields always activate when they stop.
Sonic the Comic
Flashers appeared in a few issues of Sonic the Comic, most notably in Issue #23 in the Sonic story "Pirates of the Mystic Cave". In this story, the Sky Pirate Captain Plunder had stolen several Flashers and Crawltons from Dr. Robotnik and used them to defend his hideout in the Mystic Cave Zone. When Sonic and the Freedom Fighters arrived to rescue the kidnapped Amy Rose, Sonic and Tails became separated from Porker and Johnny and ran into a swarm of Flashers. Unlike their game counterparts, these Flashers were capable of moving and maintaining their electrical fields at the same time. The swarm cornered Sonic and Tails, shocking them into unconsciousness and allowing Plunder and his pirate crew to capture them.