Let sleeping dogs lie

Let sleeping dogs lie is a recommendation to leave things as they are and refrain from discussing a matter any further for fear of instigating trouble.

To be a one-man band

“To be a one-man band” refers to a business which is run, controlled or managed in every aspect by one person alone, rather than by several people.

And pigs might fly

“And pigs might fly” is used to ironically express disbelief; when you think something is impossible or when you think a particular event is very unlikely.