Mecha sonic (MKII) is the second installment in the MK series made by Robotnik. The only difference between MKI and MKII is a new sleeker appearance and MKII has a larger capacity for chaos energy. MKII was first used to keep knuckles and sonic busy when Robotnik attempted to steal the master emerald from the floating island to power his death egg, but fortunately for sonic they both failed. (as seen in Sonic & Knuckles).