E-10000B is a blue robot that appears in Sonic Free Riders as a playable character in Team Dark's storyline. He appears to be on the same frequency as E-10000G. He also replaces Omega as Team Dark's power character. Near the end of the game, he is revealed to be Metal Sonic in disguise.
Shadow and Rouge have just come for the World Grand Prix and attempted to join. However, Omochao refused because they needed three members in order to participate. Rouge then randomly picked E-10000B who agreed to join their team. After a little while, E-10000B complained that he was tired, but was selfishly ignored by his teammates. Later on, E-10000B malfunctioned, broke down, and appears to explode. This exposed him as Metal Sonic. It is unknown if E-10000B was a disguise for Metal Sonic or if Metal Sonic somehow got inside of him.
E-10000B is the only character in story mode to not be playable in multiplayer mode, being replaced by E-10000G.