He has a bee in his bonnet (i.e. is hare-brained). [ Scotch Proverb ]

A soul only needs to see a smile in a white-crape bonnet in order to enter the palace of dreams. [ Victor Hugo ]

Modern women find a new scandal as becoming as a new bonnet, and air them both in the Park every afternoon. [ Oscar Wilde, An Ideal Husband ]

Never teach false modesty. How exquisitely absurd to teach a girl that beauty is of no value, dress of no use! Beauty is of value; her whole prospects and happiness in life may often depend upon a new gown or a becoming bonnet; if she has five grains of commonsense she will find this out. The great thing is to teach her their proper value. [ Sydney Smith ]