What's eating?

What's eating (someone)?

What's bothering (someone?) Why is (someone) in a bad mood? What's eating Terry today? I asked him how his weekend was and he just glared at me. I've never seen her act that way before. What's eating her?
See also: eating

What's eating someone?

Inf. Fig. What is bothering someone? Tom: Go away! Bob: Gee, Tom, what's eating you? Bill: Tom's so grouchy lately. What's eating him? Bob: Beats me!