Monstro was the name of the whale in Disney's animated film version of "Pinocchio". It was based on a sea creature found in the novel, The Adventures of Pinocchio.

At Disneyland in order to enter the canal boat rides of Storybook Land riders need to walk through the open mouth of Monstro. It was part of a never completed plan to create a "Monstro the Whale ride" where riders were supposed to be swallowed by Monstro and then sent on a watery ride that ended with a plunge into a calm pool.

In the original novel, penned by Carlos Collodi, the character of "Il Terribile Pescecane," the Terrible Dogfish was the predecessor to Monstro. It was described as being a mile long, 5 stories high, with 3 rows of teeth and a mouth that could easily swallow a man.

The novel "Pinocchio" has been translated into over 280 languages, which makes it the most translated non-religious book in the world along with being the most read book in history after the Bible!

More Info: en.wikipedia.org