Perhaps an even more surprising case was reported in June 2012, when a security officer at California's Monterey Bay Aquarium found a banana peel on the floor in front of the Shale Reef exhibit at 3 a.m. On closer inspection, the banana peel turned out to be a healthy, fist-size red octopus. The security officer followed the wet slime trail and replaced the octopus in the exhibit it had come from. But here's the shocking part: The aquarium didn't know it had a red octopus living in its Shale Reef exhibit. Apparently the octopus hitchhiked there as a juvenile, attached to a rock or sponge added to the exhibit, and grew up at the aquarium without anyone knowing it was there.