Meaning of you could have fooled me! in English:
you could have fooled me!
phrase
Used to express cynicism or doubt about an assertion.
‘‘Fun, was it? Well, you could have fooled me!’’
- ‘Well, with that act you pulled off, you could have fooled me!’
- ‘Well, you could have fooled me -- the humor in this book demonstrates that you are indeed a funny person.’