Brad has a thing for Mary.
Brad and Mary have a thing.
"The little angels have a thing for chocolate," Hannah explained.
It didn't have a thing to do with sex.
"Wow," she said, taken aback. "I've never heard you speak bad about anyone. You have a thing for her?"
You don't have a thing to prove to anyone except yourself.
I have a thing for retail therapy, for playing music and for drinking too much caffeine.