Newtron

The Newtron, known as Meleon (メレオン) in Japan, are first generation Badniks created by Dr. Robotnik in the original Sonic the Hedgehog video game for the Sega Genesis and Game Gear. A Newtron appear in Sonic the Hedgehog 2 (8-bit) called Meleon. It is scheduled to appear in the upcoming game Sonic the Hedgehog 4

Physical Appearance
Newtron are chameleon-like stealth robots that come in two varieties, differing in both their attack patterns and their colors: green and blue. The Newtron possess advanced stealth technology worked into their circuits that render them invulnerable and invisible until they find a worthy target. Their photo receptors, which resemble chameleon eyes, may help them target enemies from further distances.

Attack Pattern
Green: This variety of Newtron will phase out of hiding and stay affixed to that place while it fires a ball of energy toward the desired target. It will then phase back into its surroundings. Sonic found out that the best way to overcome most of these enemies was to avoid them entirely. In Sonic the Hedgehog 4, the green ones will fire themselves as missiles.

Blue: The blue variety differed greatly from the green variety in that they lacked the ability to produce balls of energy. They would phase out of their hiding place when a target approached, and then drop to the ground, gliding toward the target in a fixed horizontal line. Sonic found these enemies a bit easier to dispatch than their green cousins. This variety doesn't appear in the Game Gear version.

Sonic the Comic
Newtrons appeared in several early issues of Sonic the Comic as standard members of Doctor Robotnik's badnik army.