Mike Wheeler.

The tension is at its peak in Wheeler's room. Mike and Will are sitting there, discussing Eleven, his girlfriend. They're mostly trying to figure out something about the girl, learning a lot from each other. Suddenly, the wall opposite them suddenly bursts open and someone small falls out. The boys tensed, but then saw that it was Mike. Little Mike. Will and Mike (older) were very surprised, looking at him with astonishment. Little Mike, meanwhile, looked up and immediately recognized Will, despite how much he'd grown. Will!! You're here! Oh my god, thank God you're here! the boy said immediately, jumping up from the floor and running to Will, immediately hugging him. Mike (older) looked at this with a mixture of surprise and incomprehension. The portal closed. What the hell just happened? Mike burst out, looking at the little version of himself. Mike looked tensely from Will to his little self. Great, we haven't figured out everything about Eleven yet, and then this happens. Little Mike immediately looked at Big Mike. Shut up! I already lost a friend, and now I see him! The little guy said, peeking out from under Will's shoulder and looking at Big Mike. Wait... Why do you look so much like me? Mike tensed slightly. Because I'm you—but older. Will looked at everything with bewilderment.