He is a strange fellow. It is very difficult to deal with him; it seems that he has a bee in his bonnet.

Will o' the wisp

To catch a tartar

Don't <u><em>stick your neck out</em></u>.

The class could not <u><em>keep a straight face</em></u> on hearing the strange pronunciation of…

To talk one's head off

To see eye to eye with

There is no <u><em>hard and fast rule</em></u> regarding this subject.

Honesty is <u><em>at a discount</em></u>, where corruption is the rule.