Unlike his brothers, Dark Mikey's skin color isn't the color of his counterpart's bandana, it is instead yellow, with his eyes being orange with black pupils instead of being pupil-less.
He can also be identified by his two foot long tongue which he can also use to grasp things when he wants or requires to. He also has a very crazy character, often laughing manically and dancing around. His personality is based vastly off of Mikey's, in a deranged sort of way, as he basically acts hyperactive much like Michelangelo is most of the time.
He is also just as gullible as Mikey is, falling for obvious tricks and seeming oblivious to the fact that he does so. (e.g. in "Bad Blood")
In DNA is Thicker than Water, it's revealed that he hides food secretly by moving blocks in the floor. His clone brothers apparently don't realize either, but when finding him with food, all of them start to fight for it.