You don't say!
Stop saying that！别说了!
Sally: The Jones boys are keeping a pet snake.
Alice: You don't say.
You can say that again!
Mary: It sure is hot today.
Jane: You can say that again!
Who can say?
A: What are you gonna do? Now that you've left the company?
B: Who can say? Maybe I’ll go abroad.
Having said that
He forgets most things, but having said that, he always remembers my birthday.
Not say boo
The neighbor's daughter is just the cutest little thing, but she didn't say boo the whole time we were there.