Sonic the Hedgehog protagonist Sonic the Hedgehog, a blue hedgehog able to run at supersonic speeds, and recurring villain Dr. Eggman, an evil scientist whose ambition is to conquer the world. Among Sonic's many allies, the most well-known include: Miles "Tails" Prower, a twin-tailed, highly intelligent yellow fox who is Sonic's sidekick and best friend; Amy Rose, a pink hedgehog who is Sonic's self-proclaimed girlfriend and a hero in her own right; Knuckles the Echidna, a coolheaded red echidna who is the guardian of the Master Emerald; Shadow the Hedgehog, an anti-heroic doppelgänger of Sonic with a dark past; and Metal Sonic, a
Sonic the Hedgehog (Archie Comics) stories that fit into the series continuity. Since 2013 these issues have served as a combination free comic special with the Mega Man series; a free Sonic issue serving as a prequel to "Sonic Lost World" was also released in 2013 for Halloween Comic Fest. Various compilations have also been put together, such as the "Sonic Saga Series, Sonic Archives" and "Knuckles Archives, Sonic the Hedgehog, Sonic Universe" and standalone graphic novels, "Sonic Legacy, Best of Sonic the Hedgehog, Sonic Super Digest" and "Sonic Super Special Magazine." Following "Worlds Collide" the latter two series and the Free Comic Book Day