Why did my Pokemon stop producing eggs in Gen 2 while shiny hunting?

Question

I was breeding for shinies in Pokemon Silver using the shiny Ditto method. I had already gotten two shiny Cyndaquil nearly back-to-back after about 50-70 eggs, and then I decided to move on to Zubat for whatever reason. It had been a while, a lot longer than it took to get the Cyndaquils, when they suddenly stopped producing eggs. This happened at exactly 90 eggs, just in case the number is important.

No matter how much I ran up and down in Goldenrod, they wouldn't make any eggs, so I decided to take the Zubat I had in and replace it for one that I had hatched. Still, no eggs were made at all. I decide at this point to catch a new Zubat to try that, but still had no luck. Because of this I gave up and moved on to Totodile, and got a shiny one pretty quickly, at around 30-40 eggs. I tried coming back to Zubat but to no avail still. Then I moved on to Eevee to hunt. However, the same thing happened that had happened to the Zubats, this time at exactly 25 eggs hatched. I moved on to Charmander and hatched a shiny at exactly 6 eggs. Now I tried to hatch a shiny Mareep but the same thing has happened again, this is at exactly 21 eggs hatched.

Please someone help me out I have no idea whats going on. Before you ask, the Pokemon say that they're friendly with each other when interacted with in the day-care (Ditto had gone up nearly 60 levels by now and I don't have the kind of money to take it out of the day-care with a fee like that right now). I made an account just so I could ask this, please someone help.

Comments

I had this problem when I was playing Pokémon X when breeding for a Goomy. It took so long but after a while I finally got it. I guess you just have to be patient to get what you want. :/ Good luck!

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Alright, thanks for trying to help

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Yeah no problem. We are always here to try our best in answering. If I find anything else regarding your question, I’m sure I’ll post it here. :)

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I believe I have found an answer for you. :)

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This reminds me of my silver vc playthroughs. I put five of my six Pokémon main team in the pc at Goldenrod to transfer them to Bank. All of a sudden, they were gone. I couldn’t see them in poketransporter nor were they there when I checked the pc in-game despite many restarts. Distraught (understandably), I started over with a new save file. When I reached Goldenrod I decided to withdraw a Pokémon I had caught earlier in the new save file. All of a sudden the five Pokémon I had deposited from the previous save file were there, ready for me to use. It’s possible the answer lies with how breakable assembly code is, but I don’t know enough about it to possibly troubleshoot the source code to understand why there seems to be a limit to certain Pokémon breeding in your game. Hopefully one day a Supernerd will appear and answer all of our questions.

Answer 1

With further research, I believe I have found the answer to your question. I think I do not need to explain how breeding works because I assume you know how to breed, as you had mentioned you received an egg of the Pokémons you bred at the daycare.

So according to Bulbapedia,

In Generation II only, if the Defense IVs of two Pokémon are the same, and the Special IVs are either the same or differ by 8, they cannot produce Eggs. Because of how IVs are passed down from parents, this condition suggests the Pokémon are related.

This is why you could not receive any more eggs because the two Pokémon that you added to the daycare were “related”. Therefore, no egg can be hatched.

So, to see if Pokémon are not related to each other, we need to take a look at their individual values (IV’s). Here I will include the HP (which you won’t need because you only need to check for defense and special, but I will include it just in case) and OtherStat formula if you would like to use them. Keep in mind what Bulbapedia says and you should be good.

HP Formula
OtherStat Formula

I hope this works and helps in clearing out your confusion. Good luck!

Source 1
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Source 3
Source 4

Comments

Does this explain OP's recollection that the same Pokemon were first able to produce eggs, but then suddenly weren't able to? Are you saying their IVs changed?

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According to Bulbapedia yes.

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Am I missing something? Can IVs change in earlier games?

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Is that a new question?

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Fizz asked 2 questions, so which one are you answering "yes"?

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I'll keep this in mind if/when I start GSC hunting.

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@a baby feel free.