Cilerba is a programmer & self-proclaimed Pokémon nerd and what better way to demonstrate both than to engineer a way to catch a shiny Lugia in Pokémon Red and Blue. But wait, I hear you say, how can you catch a Gen 2 Pokémon in a Gen 1 game, let alone a shiny one? Well, that’s where arbitrary code execution (ACE) comes into play.
I wrote about some ACE a while back (see: Here’s an ACE speedrun of Lufia II: Rise of the Sinistrals that took just 195 seconds) but it basically requires some carefully selected inputs to rewrite code within the game and, in this case, Cilerba used it to create the Lugia encounter and he even included a special map to do it.
As for how you can get a shiny in Generation 1, that’s technically possible without ACE. A shiny in the early gens was defined as a Pokémon with specific determinant values (or DVs; now known as individual values or IVs). The chances of finding a Pokémon with shiny DVs in Generations 1 and 2 were 1 in 8,192 but of course, you can’t see them as shiny in Red/Blue/Yellow so you’d have to catch them and check their stats.
I won’t go into too much detail on this as not to derail from the point of this post but it can be a little tricky without prior knowledge. What Cilerba did in his case was to program the game to display the shiny with its actual shiny colour should it appear (with the regular odds).
It’s an amazing acheivement and I respect all the work and effort he put into this along with some help from others in the community. You can find the tools he used in the video’s description if you want to try it out yourself.
