Mikey can create mystic apparitions of himself, more specifically his Doctor personas.
Although they don't last for very long.
What I mean is that Dr. Delicate Touch, Feelings, Positive, and Rude are able to come into the real world as separate entities, each with a certain role to play while on a time crunch.
DDT is brutally honest, saying the truth even when the recipient doesn't want to hear them.
DF is there to gradually help a person for however long it takes.
DP is almost always present as Mikey himself, being a sense of relief in the present but not over time.
DR is Mikey's personal feelings, uncaring of others and just wanting to make himself feel better, even if it effect others in not so good ways.
And Mikey him self is the source, he's stripped down to the bone and exposed to the world as his true self.
Anyways that there roles, but in the context of the actual plot their there to help the family and Mikey make decisions.
They are chaotic, especially with multiple of them around, and are basically a layer of mystery to the power that Mikey actually holds.
At some point Mikey will feel useless, especially when a person catered to special needs is around, and the family will have to help him.
In the end, at some points, he might even hear their voices and see them in his dreams. Almost as if there are people living in his brain.
This is also where he meets the other doctors, ex. Dr. Disappointed.