Or, in other words, what is some dumb hypothesis you've entertained that you'd've turned into a full blown crackpot theory if only you were schizo enough?

Mine is that objects' gravitational fields do not end--rather, they eventually taper off to zero and then reverse, pushing objects away with more force the further they get. This would be used to explain the accelerating expansion of the universe, and account for the forces that are currently attributed to dark matter.