Before Disney bought Pixar, a script for Monsters, Inc. 2: Lost in Scaradise was being worked on by Bob Hilgenberg and Rob Muir, as the screenwriters discussed in an exclusive interview with Animated Views last year.
Now io9 shares concept art from the never-made sequel and recalls details about its plot: “The movie was to be set some time after the first, when Mike and Sulley decide to visit Boo on her birthday. But Boo has moved away from the house attached to her closet door, and Mike and Sulley decide to look for her. Once they’ve decided to seek her out, however, they can’t return Monstropolis until they’ve found her.” Quite the opposite idea of the
sequel prequel in theaters right now, but as with any idea, it would have been interesting to see it come to fruition. There was a Disney-produced script for a Finding Nemo sequel as well, although whether or not it bore any resemblance to Pixar’s upcoming Finding Dory is unknown at this point.