Mecha Knuckles was the third robot in the Metal Series created by Dr. Eggman, the most strongest out of the first three based on Knuckles the Echidna. The only game Mecha Knuckles appeared in was Sonic R, which was Sonic Racing game for the Sega Saturn.  


Sonic CD 2 Mecha Knuckles was originally going to be in Sonic CD 2 by guarding the Master Emerald, but Metal Tails took his place. There is 2 codes you enter in the Sound Test in the XBOX Edition to see his beta artwork and his secret ending.