Youtube refused to let me post this as a comment on the Catly video so I'm posting it here. I assume it was autoflagged for spam because I explained too much idk -
I do not think AI played a part in the Catly trailer at all. I don't upload 'content' on youtube/social media but I do make 3D models elsewhere.
The fur looks exactly like hair particles in the free 3D program Blender, on the cats. Video game engines can't render this, too detailed and would cause too much lag, but blender's internal video renderer can! The game itself Cannot look Anything similar to this video, though. Check back in 10-20 years. The hair on the human character, however, looks closer to card hair, that's why it sways a bit nicer while the cats look so stiff. Solid or card-based hair is the only one video games (console or computer) are able to reliably render at this time, iirc. Her clothes' folds remind me of Marvelous Designer tutorials I've seen, especially the bottom of the hoodie where they shrunk the two (front/back) bands too much and made weird wrinkles above it. Technically though, even this can be 'copied' in Blender, again for free, if you use fabric simulation well enough, just not quite as easily. I think she's the only "actually might be in the game" model on here. She does have 4 fingers and 1 thumb, if you really zoom in, it's just they're posed a little awkwardly in some spots. The visor that's in every outfit is probably partially because they couldn't get a human face to look right, or possibly ran out of time to even model/rig/animate the thing and put a bandaid on it. The 'dreamy' effect they were going for also backfired, they put emission on everything with a high bloom along with the too-limited colors, so it is reminiscent of AI's blurriness but is not. So the game will not and can not look anything like this, as far as the cats go, but the human might look same, possibly just at lower polycount. You can see in the cats blinks how the rigging is lazily done (around 0:22), and along with how static the human's clothes-show-off segment is, I think the rigger/animator(s) on this project were very tired, and likely very over-worked by the time they finished combing all that cat fur. Yes, you have to 'comb' hair/fur particles to make them go in certain directions; it does not mix well with physics, which is another reason the cat's fur is all very stiff. The camera work too, being so un-natural, is because the camera in blender has a really weird pivot/rotation system and they probably had the animations for that on bezier instead of linear or something. They also didn't add any 'noise' to the animation to make the camera slightly wiggle, making it even more stiff and strange. Although this trailer indicates absolutely nothing about what the game will be or even look like, I feel like that's not a first in the gaming industry.
All in all, it looks kinda bad, but… entirely do-able, in Blender, entirely for free. They were probably underpaid, but real people did make this. To the Catly creator(s): please god release a unshaded/untextured/wireframe "behind the scenes" image of these things. It'd fix so much for you. NFTs are a wretched scam, but your employees don't deserve this.
TL;DR
Blender is a great free 3D modelling and animation program, I'm sure that's what they used, they just chose a really bad art style for this.