a "mike crush" is a type of crush you have on someone that is nice to you when they don't have to be. and all you can think about is sleeping with them to repay them for their kindness.
ex 1: oh that kid was so nice to me on my first day of work while everyone else didn't even notice that i was there! i think i'm starting to have a mike crush on him.
ex 2: i just dropped a dime and that guy just picked it up and handed it back to me. total mike crush.