Stop N' Swop

It is believed that Stop N' Swop had originated from Rare's games Banjo-Kazooie, Banjo-Tooie and Donkey Kong 64. However, recent discoveries were found that lead to finding the true origins of Stop N' Swop, and it all leads back to Nintendo's premier game Super Mario 64. Stop N' Swop was supposed to be a feature meant to link Rare's then upcoming game Banjo-Kazooie to Super Mario 64, but was retooled for Banjo-Tooie and Donkey Kong 64, and was then scrapped when newer Nintendo 64 consoles had been released.

Backstory
Rare had been partnered with Nintendo from 1994-2002, before Microsoft had taken their hands onto Rare. As such, the company had access to technology that was used to make games for Nintendo consoles, Along with that, Rare had also used SGI systems to create the graphics for SNES games like the Donkey Kong Country trilogy. It is no coincidence that both Rare and SGI would be given access to development of Nintendo 64 games and the console itself, respectively.

Nintendo wasn't too sure of using the personalisation A.I. that came with Super Mario 64 and giving a bit of it to Rare at the time, so they didn't give the secrets to said company when it developed the game Diddy Kong Racing. Once the success of the game had blasted off, it was only then did Nintendo had given access for Rare to the A.I. when development of Banjo-Kazooie was under way. It was the most stable choice for Super Mario 64, as both it and Banjo Kazooie were 3D platforming games.

Since Banjo-Kazooie was the choice that was most obvious for the company, Nintendo had then given the developers of Banjo-Kazooie a way to share the coding of Super Mario 64 to it in order to link both of the games together in order to unlock stuff from both games. It was given the name of hot swapping. This process involves turning on the console with one game playing, then switch said game cartridge with another one in a ten second time span. This allowed for the RAM to be stored for one game and then be transferred to another in order to add surprises to both games.

However, early tests for this feature had caused strange, unusual phenomenons for both Banjo-Kazooie and Super Mario 64. These unintended side effects caused by the A.I. of Super Mario 64 had made Nintendo and Rare scrap the idea of linking the two games together. Rare then used the idea of swapping cartridges for their own games in the form of "Stop N' Swop".

As probably due to the result of what happened to Banjo-Kazooie and Super Mario 64, Nintendo had released newer versions of the Nintendo 64 console with the hot swapping time span being reduced down to one second. This had made the "Stop N' Swop" feature for Rare's games virtually impossible to pull off.

The Stop N' Swop Phenomenon
The requirements of pulling off the Stop N' Swop effect are a lot. Console-wise, it is required to have an older version of a Nintendo 64 console(with a Rumble Pak if a game that fits the criteria requires it), so it is possible for hot swapping to occur. Along with this, it is also required to have any copy of Super Mario 64, as every copy of it is personalized.

For any other game to pull off with Super Mario 64, there are types of game that this effect can only work on. One such type would be any first or second party Nintendo 64 games. Another type would be any game that's a 3D platformer, regardless of any party affiliation. Prototype cartridges also have to follow these said rules too.

The order of swapping cartridges can be in both orders (Super Mario 64 -> [INSERT GAME HERE], and [INSERT GAME HERE] -> Super Mario 64), as both cartridges would be affected by the process of hot swapping.

Once this process has been finished, the Stop N' Swop effect can be executed for both cartridges. Any game that doesn't follow this criteria would not have these effects shown.

The True Reason Why Nintendo Updated Their Consoles
The enclosed reason why newer Nintendo 64 consoles were updated to nullify hot swapping was stated to be that swapping cartridges in this way would potentially damage the console. However, considering that this had happened coincidentally after Banjo-Tooie had been released, it is reasonable to assume that this was because children might swap Rare's games with Super Mario 64, causing the personalisation to affect both cartridges. It could be a way to cover up another part of the perosnalisation mechanism that was in the game.

Why Super Mario 64 Can Be Swapped with Other Cartridges than Banjo-Kazooie
Since the requirements for hot swapping Super Mario 64 with other game cartridges include games other than Banjo-Kazooie, it is reasonable to assume that the working and testing for swapping both Super Mario 64 and Banjo-Kazooie was short-lived. This could mean that there wasn't any coding to lock out any other cartridges from swapping with Super Mario 64 besides Banjo-Kazooie.