Have a thing for someone
I had a thing for one of my teachers when I was in college.
Have a crush on someone
I had a crush on one of my teachers when I was in college.
Have a thing about sth.
She's got a thing about spiders - she won't go near them.
Make a big thing out of
We had a little kiss, so what? I don't know why you're making such a big thing of it.
The thing is...
I’m sorry I didn’t call you. The thing is, I’ve been really busy lately.