Also, this is a really specific use case, but I can also find a use for this in the summer events archive thread, which can potentially help other users who want to dress up their pets as the event NPCs. When I list NPCs, I also link to where they can be found in the Archive, but sometimes it can be tricky to distinguish certain littermates from each other, especially since the NPCs may be wearing items that cover up the more distinguishable parts of their bodies! Right now, in the cases where I think it may not be obvious (to someone with a good monitor and no color vision issues, admittedly) which outcome a pet is, I write "adult at age 23" or something in the thread.
e.g. there's this NPC, Marcus, from the Egypt Event in 2014:
Marcus's litter is found in October 2011. The outcomes are really similar, and Marcus is wearing clothes that cover one of the features that separates him from the others: the dark spots on his shoulders. So I wrote "adult at age 23" in the thread when I listed Marcus. But this won't be enough for pets that grew up on the same days--e.g. the robot dogs from January 2009 grew not only into adults but also into puppies on the same day, so if we ever get an NPC that's one of those dogs and most of the gold-vs-silver bits are covered... -sweatdrop-