Stone the crows
Definition 1 of 2
Pro Tip 1/3Emphasize Surprise
Use it to stress your shock or unexpected amazement at something. 
Stone the crows, there's snow in April!
Pro Tip 2/3Rarely Used
It’s an old-fashioned phrase and not common in modern English conversation. 
I guess I'd say 'stone the crows' if I were in a period drama.
Pro Tip 3/3Not Literal
Remember, it’s not about actual stones or crows. No harm is meant to birds! 
Stone the crows, is that your car? It's huge!