"You know what thought did? He didn't do anything - he just thought he did." A piece of nonsense which basically points out the futility of thinking that something has been done without actually going and assuring oneself that it has in fact been done.
'A Classical Dictionary of the Vulgar Tongue,' 2nd edn., 1788: 'What did thought do?
i heard it go like this...........'You know what thought did.........followed a muck cart and thought it was a wedding........... no he didnt ....he only thought he did!'