Stop N Swop was a feature that was planned for Banjo-Kazooie and its sequel Banjo-Tooie, and would allow players to unlock content between the games by quickly swapping cartridges out.
Developer Rare based the idea around a quirk in the Nintendo 64’s hardware, in which any time the console was turned off it still retained the contents of its memory for a number of seconds.
The idea was that players would reach a point in a Rare game then turn the console off, quickly swap the game out for a different Rare game then turn the console back on. If performed correctly, the stored memory would be detected by the second cartridge and would unlock new content.
Stop N Swop was ultimately abandoned but players continued to spread rumours about it, mainly because a menu called Stop N Swop appeared when players collected a special egg after completing Banjo-Kazooie.
A variation on the feature was eventually implemented in the Xbox 360 re-releases of Banjo-Kazooie and Banjo-Tooie, but until now nobody’s been able to show it working on the original Nintendo 64 version.
Modder Skawo has now managed this, showing the trick in action on retail Nintendo 64 hardware in a new video.
After playing through Banjo-Kazooie to prove the Stop N Swop content hasn’t been unlocked yet, Skawo inserts a flash cartridge including a customised version of The Legend of Zelda: Ocarina of Time that they modded.
The modded game runs a cutscene in which Link explains the history of Stop N Swop, before copying the required unlock information to the console’s memory and keeping it there.
Skawo then quickly turns off the console, swaps the cartridge for Banjo-Kazooie and turns the console on again. The hidden content has now been unlocked in the game.
According to former Rare employee Paul Machacek, Nintendo asked Rare to remove the feature because it was worried about the console or cartridge being damaged, and that it couldn’t guarantee it would work with hardware revisions.
The latter would prove true, when later N64 consoles received revised motherboards which only stored the memory for around a second after powering off.