Unfortunately, you will only find out about the megacrush well after the window of opportunity. This information will haunt you for the rest of your days.
Girl: Hey, I just rented Scream, and I'm too scared to watch it by myself. Do you want to come over and watch it with me?
Boy: Nah, Dave and I are gunna go play Mario Kart 64 tonight.
Girl: Oh... ok...
Dave: Hey dude, remember back in high school that girl Kate?
Moron: Ya, she was hot.
Dave: Ya, she had a megacrush on you dude. Did you ever get some of that?
Moron: wtf! She had a crush on me!? I am teh fail!