I'm a nerd for old lore, piecing together what they originally had conceptualized in their planning process when creating Pokemon RBG/the sequels.
For example
--Scrapped town called 'Town C' in early alpha. I believe it has a flight path in the original games. The town has a truck, the same truck you find in Vermilion city harbor. My headcannon is the St Anne was not supposed to be a one and done, you were supposed to travel on it to town C and then from there you were supposed to go to Celadon.
--The Viridian Gym was supposed to be the 1st gym. It had a kid gym leader. Yujiro. Not sure what his specialty was supposed to be. Looks like his sprite got recycled into Giovanni which is interesting because that sprite ended up being the Viridian Gym leader anyway.
--The original trainer had a whip and looked completely different. The shrinking animation still has this sprite albeit blacked out.
--Lorelei and Agatha were in Gold/Silver originally. Lorelei's sprite got recycled as Karen. I think they found Lorelei redundant with Pryce. I'm not sure why Agatha was replaced.
--Agatha was actually featured in a few different versions of early builds. She was found in a house chilling, but her dialog was missing. Not sure what plans they had for her, maybe just a simple "im retired"?
--Piggybacking off of those two, I heard theories that Giovanni and Misty were originally supposed to be in the elite four for Gold/Silver. If someone heard that too I am super curious what your thoughts are.
--Imposter Oak was originally part of Gold/Silver as a villain. Not sure how he was incorporated into it, but I find it fascinating that he was actually part of the game. I've always found his card to be random as fuck because he's never really been explained or seen in media.

Please post all the theories you have that make sense. I appreciate you.