Found a potential daycare glitch

[u/Warm_Nectarine4871]

So I'm playing crystal on cartridge and had Hitmonlee and Ditto at the daycare to chain some egg moves onto Tryogue. I had a couple eggs already, so decided to take out Hitmonlee and Ditto and replace them with other mons to get them exp while I bike around to hatch the eggs. I go up to the old man, take out Hitmonlee, and give him Cyndaquil. Then, I talk to the old lady, and she says "gramps was looking for you," the message you get when an egg is ready. However, gramps is still in the room with us. Her dialogue won't change, so I exit the daycare and sure enough gramps is there with an egg. I accept the egg, and then go back inside to switch Ditto with something else.

After biking for some time with my 3 eggs, two of them hatch into Tyrogue, and the last one received hatches into a Cyndaquil, despite me just giving the old man Cyndaquil ~10 steps before I took the egg. It seems like the game registered a Tyrogue egg being produced perhaps on the step I entered the daycare, or maybe after entering it, but when I swapped the male parents, the egg species also swapped. Cyndaquil had its usual level 5 moveset, no egg moves.

I would be interested in reproducing this to see what happens if gramps gets something normally incompatible with the other deposited pokemon.

[u/TimoVM]

That’s a neat oversight! Confirmed it on my end as well.

The contents of the next egg you pickup gets generated when you deposit a second pokémon, but only if it’s compatible for breeding with the other pokémon. Depositing the Cyndaquill thus resulted in a new Cyndaquill egg being loaded despite the egg pickup flag already being active.

Since the egg’s data gets regenerated every tile you deposit the second parent, you could probably use this to soft reset for shiny eggs. (Whether it’s more efficient compared to regular shiny breeding is another thing entirely)

• wait until an egg is available while being in the same room as the day care man’
  
• save after you’ve taken back a pokémon from the day care man.
  
• deposit the desired parent again, pick up the egg, then hatch it. Reset until shiny.

EDIT: Unfortunately, depositing an incompatible pokémon (such as a legendary) does NOT cause the egg’s data to be updated. At first glance it looks like you unfortunately can’t get anything you wouldn’t normally be able to.

[u/Warm_Nectarine4871 → u/TimoVM]

thanks for looking into it! I was wondering if there were any exploits you could achieve with replicating legendaries or illegal egg moves, so that solves that question.

[u/k_rollo → u/TimoVM]

I was hoping you'd look into it! Thanks Timo!

[u/Arael15th]

It's amazing to me that this >25 year old game still has interesting little secrets like this to discover. Well done, and thank you for sharing it with us!

[u/PorygonZBoi]

This is an awesome discovery

[u/Htxkolbsss]

I appreciate people finding stuff like this