Ever since the release of Banjo-Kazooie and Banjo-Tooie back in the good old N64 days the hunt for the mysterious device within the game known as Stop n' Swop. Stop n' Stop was a play mechanic that was meant to connect the two games together through a process known as hot swapping. Hot swapping required the player to remove one cartridge from the console and inserting the other within a few seconds without turning the power to the console off. Now Rare had announced their plans to do this before the release of the original Banjo-Kazooie game and that's where the problem began as Nintendo had a bit of a problem with this concept as it seemed that the process of hot swapping wasn't exactly good for the N64 console and even created the possibility of ruining the players console. With that Nintendo decided to put an end to Rare's plan which was probably the right choice but by that time Rare had already finished the development on Banjo-Kazooie with all the mechanics required for hot swapping included. So what did Rare do? They tried to hide the evidence but ended up doing a plain horrible job of it creating possibly one of the biggest game investigations in the history of gaming.
Now I'm not going to get all technical with this as I'm no hacker and half the stuff I've read on this subject related to hacking has only left me more confused. The bottom line is that Rare did a horrible job of hiding the items required for the fabled Stop n' Swop which was comprised of six multi colored eggs and an ice key. These items were left in the game itself and only required the proper codes to be inserted in the sandcastle cheat room within the game in order to allow them to be acquired which would then add them to your statistics screen under the label of Stop n' Swop. These codes were however not given within the game but were at some point found when the game was being hacked however they are quite easily acquired now and are believed to have been the codes used for the testing of the eggs when the game was in production to to the simplicity of the codes. The method in which these items would have originally been unlocked is still unknown as the true method was either completely removed or hidden to the point where it no long operated without the codes.
Rare left one other major clue to Stop n' Swop within the game in the form of the video sequence after finishing the game 100% which had Mumbo show Banjo and Kazooie a photo displaying the locations of two of the eggs as well as the ice key. Of course the items weren't accessible but why exactly was that video not removed? I can't believe that they just forgot to remove a clue as big as that but instead I believe at that time they were still planning to go through with Stop n' Swop and the true method of unlocking said items was to be hidden within Banjo-Tooie. It was either that or Rare just said screw it we'll put the game out the way it is and just drop the whole idea in the next game. Either of those are completely possible but the first just seems a lot more likely.
Were there originally only two eggs instead of the six that were found throughout the game? Or was it that those two eggs and the ice key were the only items that were originally able to be unlocked within the first game while the other four eggs would require you to link up to Banjo-Tooie to unlock? Much of this is still unknown but there are many other clues as well as theories that may connect to Stop n' Swop