(well,) imagine that! spoken
Used to express a surprise or astonishment, particularly in response to the information which has been recently revealed.
He has been awarded the Nobel Prize for literature. Well, imagine that!
Her grandfather made a recovery after undergoing a tricky operation. Imagine that!
To be surprised by some sudden occurrence
To greatly surprise, shock, or confuse someone
If you fall for someone's trick the first time then they are at fault.
Are you going to mess with me again? Fool me once, shame on you; fool me twice, shame on me.