Yeah, I once read about a "mystery" in a lab that was researching aquatic creatures...crabs kept turning up dead, like fucked up, ripped apart, dead.
All animals were kept in seperate tanks, according to type and size.
Turns out an octopus had been climbing up and out of its tank, across the tank air pumps, into the crab tanks to eat them...
Then there's that crazy shit they do where they like immitate a fish n stuff like this one
http://www.youtube.com/watch?v=ygh1-ul6E94
I totally love the way they move around too, I'd love to get one.