The idea for Stevenson dates back to early drafts of the Muppet Treasure Island script, in which the first idea for Long John Silver's sidekick was a female parrot named Amazonia. Amazonia had something of a flirtatious relationship with Long John. The character was changed in a later draft to a male parrot, Stevenson, who would complain about the differences between the book and the movie. Eventually, the character evolved into Polly Lobster. 
However, the idea for Stevenson was picked up and used for the CD-ROM game.