Most two dimensional Sonic titles are sidescrollers. Their controls are fairly basic and do not deviate much from the genre standard. The selling point of the series is the incredible speed of the playable characters who usually have the ability to run uphill, up walls, and even along ceilings. Rollercoaster-like loops and corkscrews are also common in Sonic games, as well as springs that shoot Sonic in certain directions. The stages are also similar to rollercoasters in that many sequences involve Sonic being thrown along preset paths with little input from the player, which has led to criticism that the player can complete a Sonic game merely by holding the pad in one direction. The games also feature numerous sections involving precise jumping between platforms and avoiding hazards, although these sections do not require "pixel-perfect" judgement and are perhaps more lenient than most platform games of the era. Despite these criticisms, Sonic the Hedgehog is one of the most recognizable characters in the gaming world.
Sonic is renowned for his incredible speed. It is through this "supersonic" speed that he receives his name. Sonic is also invincible when spinning, whether in the air or on the ground. Sonic acquired his famous spindash move in Sonic the Hedgehog 2.
Sonic's personality is like the embodiment of wind, as he is carefree, and treasures his freedom greatly. Sonic has a love for speed, able to outrun the speed of sound, and can be a little impatient at times but he will always be there if his help is needed. He is also very courageous, and he never backs down from any challenges, no matter how difficult.
Sonic's best friend and lifetime sidekick. He made his first appearance in Sonic the Hedgehog 2, where he could either be playable on his own or would follow Sonic around and assist him in attacking enemies. However, this proves to be uneffective in attacking badniks, and more useful for fighting Bosses. Tails was the nickname given to him due to the fact that he has two tails. He uses these tails to attack enemies and fly. However, he could not fly in sonic the Hedgehog 2 although he would occasionally be seen flying down to Sonic after getting lost. Tails has developed into a character with incredible intelligence, flying and building planes, robots and mechs, even though he is noted to be much younger than the rest of the Sonic The Hedgehog cast.
Sonic first met Knuckles in Sonic the Hedgehog 3. In this game, Dr. Eggman meets Knuckles and learns that Knuckles guards a set of Chaos Emeralds, powerful gems that he plans to use in order to power his damaged weapon, the Death Egg (an obvious parody of the Death Star). Eggman tricks Knuckles into thinking that Sonic and Tails were going to steal the Emeralds, and he was trying to protect it. Knuckles eventually learns that Eggman had deceived him in the sequel Sonic & Knuckles, when Eggman steals the Master Emerald, a gem Knuckles guards. Sonic and Knuckles joined forces reluctantly, and got the Master Emerald back. Since then, their relationship has become more of a friendly rivalry.
 Amy Rose
Sonic's self-proclaimed girlfriend whom he first met in Sonic CD. Sonic is pretty annoyed with Amy's constant advances to marry him. However, he is grateful for all the times Amy has helped him, such as when Amy broke a framed Sonic out of prison in Sonic Adventure 2.
 Cream the Rabbit
Cream is Amy's best friend and she rarely interacts with Sonic, although they are friends. In the Sonic Rush series, Cream was Blaze's best friend. Also, Cream is seen a lot with Cheese the Chao.
 Blaze the Cat
Blaze is a princess from an alternate dimension, Blaze first met Sonic in Sonic Rush when both their dimensions were in flux. In that game, she was the guardian of the Sol Emeralds, her world's version of the Chaos Emeralds. Sonic and Blaze met again in Sonic Rush Adventure, but this time Sonic was in Blaze's dimension. He helped Blaze get back the Jeweled Scepter.
 Silver the Hedgehog
Silver is a hedgehog with psychic powers who hails from the future. Sonic first met Silver in the Xbox 360 and PS3 only Sonic the Hedgehog. However, due to the game's events, they first met in the PSP exclusive Sonic Rivals. The only 2 times Silver appeared on a Nintendo console was in Sonic and the Secret Rings in Party Mode and Sonic and the Black Knight in Multiplayer Mode.
edit Enemies and Rivals
Originally known as Dr. Robotnik, Dr. Eggman is Sonic's first, and most persistent enemy. In more recent games however, Eggman is usually not the final boss, despite being the primary antagonist. As such, he and Sonic were sometimes forced to join forces in order to stop a greater evil.
 Shadow the Hedgehog
Sonic first met Shadow in Sonic Adventure 2. In that game, Shadow framed Sonic for stealing a Chaos Emerald, due to their similar appearance. By the end of the game, Sonic and Shadow joined forces in order to stop the ARK from crashing into Earth and destroying it. During this effort, Shadow seemingly sacrificed himself. However, he later returned in Sonic Heroes, but with amnesia. Shadow's true origins weren't revealed until the spin-off game, Shadow the Hedgehog. Since then, he has become more of a rival with Sonic rather than an enemy.
edit Super Smash Bros.
Sonic was the second third party character announced for Super Smash Bros. Brawl while. His attacks have been recreated just for Brawl, and is presumably the fastest character in the game. Sonic's Final Smash is using the chaos emeralds to turn into Super Sonic.