I've heard that in one of the original movies, with Buster Crabbe, they did a fight with an octopus by filming it backwards. Buster, in real time, wrapped the flacid pseudopods around himself, ending up in a horrible pickle. Then it was viewed in reverse, and it looked as if his great strength had conquered the beast.
The octopus later said that in a real fight he could have taken Crabbe with four hands tied behind his back.