Permanent Kittens
It seemed a good idea at the time… no, wait, people did freak out at the concept of genetically engineering cats who would never move past the kitten stage. But there were arguments for it, not least of which was the one that if you’re going to genetically engineer animals, it’d be best to ensure that they were sterile. Which is obviously what was going to happen, here. Also: the process of creating Permanent Kittens is extremely involved and multi-generational; keeping a stable supply of them around requires conscious effort on humanity’s part. But, really: it all came down to people wanting kittens that never grew up.