When you have a crush on someone similar to what middle-schoolers go though when they like someone. You start texting, hugging awkwardly, getting butterflies and stumble with your words every time you talk to set "crush." IM-ing is also key to Middle School Crushes (and don't forget to send lots of smiley-faces in them :) )
Absolutely no maturing in your flirting and feelings in this type of crush.
You know...I like-like that guy. Oh my goodness, I totally have a Middle School Crush on that guy!