This reminds me of a mind-blowing story I once heard from a labmate of mine, who used to work at the Monterey Bay aquarium. They had this beautiful petting-zoo tidepool display, where kids could come and touch starfish and sea cucumbers and the like. But every couple of days, an invertebrate from the tidepool would disappear. They figured the thief must be working at night, so finally they put the tidepool under video surveillance to catch him or her in the act.
When they checked the tapes, they caught their thief: an octopus living in a display tank opposite the tidepool. Every night, this wise guy would wait till everyone went home, then squeeze his way out of the top of his tank. He'd climb carefully down the side of his tank and walk over to the tidepool display, where he'd find himself a tasty, defenseless snack. The octopus knew that if he stayed in the tidepool display too long, he'd get busted, so he made sure to get back to his tank before any of the humans showed up in the morning.
While we're on the topic, have you seen this amazing video of an octopus in camouflage? Watch as the diver, David Gallo, approaches very slowly, until finally the octopus decides he's been spotted and opts for plan B.