I think your cat has worms
Why Does My Cat Drag Her Butt Across The Carpet?
It all depends on how old your cat is? Could be anal sacks, for that you need to take your cat to a vet.
The dog may have worms and is trying to alleviate itself.
One of my 3 indoor cats who is 1 year drags his butt across the carpet after pooping. They all eat the same thing and use the same box that is cleaned twice a day. Help