Video Game Secrets

[Vipershark]

the use for the eggs and key was intended to be the stop 'n' swop feature, where you had to take Banjo Kazooie out of the n64 and then put Tooie in and the data of the eggs/key would transfer over somehow and unlock features. But nintendo made a decision with the n64's design that made it so you had a very short amount of time to do this, making it nearly impossible to swap the game packs in time. So Rare had to scrap the idea and just put the transferable items in game packs that you could find in game in Tooie.

the way it worked was that with the original n64 design, any data would stay in ram for up to one minute after pulling a game cart out with the power on.
Stop n Swop was going to take advantage of this and make it so that if you do something in Kazooie, pull the game out, and the put in Tooie in under 60 seconds, the data still held in ram would be transferred over to Tooie to unlock stuff.

Nintendo later redesigned the hardware of the N64 which drastically cut the data hold time down to around 5 or 10 seconds or something, meaning that most people couldn't swap games in time so they had to can the feature.

This "ram trick" works on the Sega Genesis as well. For example, if you enable level select in Sonic 2, hold down the A button, pull the game out, put in Sonic 3, and then soft reset while still holding down A, level select would be enabled in Sonic 3 without having to do the nearly impossible sound test code.