An octopus named Sid spent 5 days on the lam after escaping from his tank in a New Zealand aquarium. Sid managed to elude detection for those days by hiding in a drain that pumped fresh sea water into the aquarium. He was caught after being spotted making a dash for an open door. Though hungry, Sid was unhurt. The aquarium staff decided that it was best to release Sid, who is an older octopus, back into the wild.
Additional story: http://www.abc.net.au/news/stories/2009/02/13/2490473.htm
For more information on octopuses, read Animal Fact Guide’s article, Common Octopus.