I remember when Conker's Bad Fur Day came out on the Nintendo 64. The cute little squirrel from Diddy Kong Racing got his own little adventure/platformer in the style of Super Mario 64. He just had an attitude adjustment and got dropped off in a dark gross-out world that received rave reviews and an M rating. You get a good sense of the game in the prologue.
You know you're in for something twisted when you mount the star of your previous smash hit on the wall. Poor Banjo. Rare clearly wanted to do something dark and different with the platformer and the new Conker character wasn't so established that he couldn't take a darker turn.
But that wasn't how the game was originally designed. New footage has emerged of the first thirty minutes of the original Conker 64. The adorable squirrel was set to star in a candy-coated adventure called Twelve Tales. He even had a little green sparrow as a sidekick and collected rainbow balloons for bonuses. Some of the same gameplay elements are there (the scarecrows were the training character in Bad Fur Day and the level design is similar), but the tone is so different as to be totally unrecognizable.
My best guess is that somewhat at Rare was worried about releasing so many cute platformers for the N64. They had other more mature titles come out at the same time--Jet Force Gemini and Perfect Dark were well-received shooters--but their platformers were taking on a certain sameness. Banjo Kazooie was cute. Most of their Gameboy Color games were cute. Even Donkey Kong Country tipped its hand toward silliness with the newest additions to the Kong family. Reskinning/rewriting Conker 64 meant releasing another tight platformer that would stand out from the crowd.
The risk paid off with good sales and even a port for the XBox with all new features. Plans for a sequel, however, were dropped. Who knows if Conker could show up again in the future? His one big title was quite innovative in its animation and gameplay mechanics at the time. Rare, now owned by Microsoft, is only developing games for the Kinect. Could a return visit from Conker happen for the interactive console?