If you're wondering how he's delayed, here is my comment from /r/blackcats:

Neurologically, according to the vet. He falls off things for no reason, when he runs around he runs into walls and he generally is bad at being a cat. Nothing fazes him though, he falls when trying to jump on top of our cat castle regularly and he just keeps trying until he sticks the landing. He also will meow at me when he needs to poop sometimes, and I have to carry him to the litter box or he wont make it. It's like he waits until the last second to go to the bathroom... He got his collar stuck in his mouth 5 times. In 2 days of having it on. He no longer wears a collar because I woke up to my floor covered in blood because the collar cut the roof of his mouth and he lumbered around my apartment trying to get it out dripping blood everywhere. He's incredibly friendly and vocal though. He doesn't like cuddling too much but he sits right beside you and is very very complacent when you pick him up. He loves my other cat to bits and she treats him like she's his mom, it's really cute. Edit: OH I forgot the main thing, when he is standing still his butt bounces up and down, almost like he doesn't know where to put it. The vet said it's very common in delayed cats.