Bit of an odd idea I've been jostling around up in the confines of my noggin after watching a documentary on Laika, with the contributions that dogs and various other animals have made (albeit indirectly) to our understanding of space travel and it's effects on organic meat creatures why haven't there ever been any equivalent in KSP? I know Kerbals are a dime and dozen and the mortality rate for your average Kerman is quite horrifying as it is so there's not a lot of reason to use animals in place of Kerbals but I think adding Kerbalized dogs or animals as alternative crew members could bring some interesting gameplay to KSP2 especially with the game's upcoming features with colonization and in slightly more macabre note could even work as an accessible form of nutrition for colonies or large ships if life support does become a thing. They would also be in general being very cute to look at from time to time, which is definitely the most important reason.
Plus there is a psychological component to this that is clearly backed up by science because as long as I say that it totally is. If there happens to be a Kerbal-Dog as part of the crew on a vessel there would be much more incentive for us to be more strict with crossing our T's and dotting our I's when it comes to making everything functions as intended and remembering to bolt a parachute on the thing somewhere. Don't want that blood on your hands, or powder depending on what led to the poor thing's demise.
Yes I was also tempted to call Kerbal dogs "Kooches" after the word Pooch but then I realized that means something entirely different and even with the context would still sound rather risque wouldn't you say? Although I'm also very certain that a noticeable percentage of this community would be more then happy to see those too added the game.