All my ideas about Flea Circuses came from how they were portrayed in cartoons. So I always thought they were imaginary. It took me years to find out that Flea Circuses were actually something people would pay to see. I guess I assumed that the whole thing was done with trickery (and I think some circuses are), but it looks like they actually attached tiny wires to the little guys and made them do tricks.
I have yet to see one in person, but this classic newsreel footage from 1949 gives me an idea of what I am missing.
[via] British Pathé