the bee's knees
If you say that something or someone is the bee's knees, you are saying in a light-hearted way that you like them a great deal. This expression is used in British English.

Back in the '80s it was the bee's knees but now it looks horribly out of date.

I bought this white sweatshirt - I thought I looked the bee's knees.

have a bee in your bonnet
If you say that someone has a bee in their bonnet about something, you mean that they feel very strongly about it and keep talking or thinking about it. This is often something that you think is unimportant. This expression is considered old-fashioned in American English.

I've got a bee in my bonnet about the confusion between education and training.

There was no arguing with the boy when he'd got this bee in his bonnet.