From Longman Dictionary of Contemporary Englishwho would have thought?who would have thought?SURPRISEDused to say that something is very surprising Who would have thought she’d end up dancing for a living? → think
Examples from the Corpus
who would have thought?• Yet who would have thought I would talk to myself in this way in these notes? he wrote.• The girl was carrying a latchkey; she let herself into the cabin. ... who would have thought of that?• But who would have thought that a humble human could do these calculations?• That's the only bait I didn't have but, who would have thought that with ice about? 