Pokemon G/S/C - A look at the inner-workings of slot machines
This video covers the different mechanics involved in Pokemon Gold, Silver, and Crystal slot machines, including the odds of lining up different symbols under each of the possible playing modes and conditions.
The soruce code can be found here:
https://github.com/pret/pokecrystal/blob/master/engine/slot_machine.asm
Pseudo-code (includes inconsequential stuff regarding delays and reel speeds, and it's also a bit dirty; you should probably just watch the video) - https://sites.google.com/site/crystalglitchystuff/research/gsc-slot-machine
In other news, if you remember my previous video where I programmed the Snake game into Pokemon Crystal, I put up a detailed article explaining how it was done around two weeks ago now. It's available here - https://sites.google.com/site/crystalglitchystuff/articles/snake