bee in bonnet

a bee in (one's) bonnet

An obsession, often with something that is strange or a source of agitation. Ever since the blizzard last year, Dad has had a bee in his bonnet about moving to a warmer climate. It seems that Mike still has a bee in his bonnet over the criticism he got in the staff meeting.
See also: bee, bonnet
Farlex Dictionary of Idioms.

bee in one's bonnet

a single idea or a thought that remains in one's mind; an obsession. (*Typically: get ~; have ~; give one ~.) I have a bee in my bonnet over that cool new car I saw, and I can't stop thinking about it. I got a bee in my bonnet about swimming. I just wanted to go swimming all the time.
See also: bee, bonnet
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • a bee in (one's) bonnet
  • a bee in bonnet
  • bee in one's bonnet
  • bonnet
  • have a bee in (one's) bonnet
  • have a bee in your bonnet
  • get worked up about (something)
  • get worked up over (something)
  • as busy as a bee
  • be (as) busy as a bee