august/september rarities

[King Scotty]

whoa--
are there usually that many uncommons in August and September?


(i'm especially surprised by the staff dogs, thought those are always common....)

[Shinryu]

Hey there;
Rarity is mainly calculated by comparing two numbers with each other: first, the number of active accounts on CS, and second, the number of pets on those accounts.
The idea here is to check how many pets are currently in circulation, and how many people are potentially going to want to trade for them.
So if, for example, there are less copies of a specific pet than there are active users, this pet would be on the rare end, whereas if there's a lot more copies of a pet than there are users, it would be quite common.

Now, rarity can partially be influenced by the probability that newborns have to grow into certain outcomes. If a pet is set to have a low chance of turning into an outcome, that's one way for the admins to influence it to be less common.
But the exact rarity of a pet isn't set ahead of time at all: it depends on the amount of pets that get adopted by users.
The same pet could end up rare, or just uncommon, depending on how often the litter was adopted - because obviously, if more users adopt the newborns, it increases the odds that people get each of the outcomes.

Staff litter pets are all set to be equally rare compared to each other. Meaning, a newborn you adopt has the same chance to grow into any of them.
But their actual rarity is additionally decided by how rare they are compared to literally every single other pet on CS.
If the staff litter this year ended up uncommon, it simply means that it wasn't adopted often enough to result in numbers that match those of other, common pets.
If there are more users than there's copies of each outcome, that makes the outcome less common overall, regardless of how likely your pets were to grow into it.

The same would apply to the other, non-staff litters as well.
A lot of people have remarked that we got a lot of uncommon pets this year indeed, so you're not the only one who finds it strange.
But explanation-wise, it really just comes down to adoption numbers versus user numbers.

I hope that explains it a bit!^^