So this is a somewhat overdue wtf but I thought I'd share.
I've got 6 cats. I used to have a dog as well, but it passed away a year ago at a ripe old age of 17.
Now one of my cats used to always walk with us if I went out to walk the dog. She'd just follow the dog. She wouldn't pee or poop like the dog did, she'd just go along for the walk.
Now ever since my dog died, she stopped walking with me when I take a stroll outdoors.
However, ever since, one of my other cats has started following me whenever I go take a walk. Not only that, but she does her crap outside at the doggy park. She neatly digs a hole, poops in it and buries it. She doesn't use the cat litterbox anymore, but instead nags at the front door when she needs to go, just like the dog used to do. Note that I have a cat door and my cats can go in and out freely, but she insists I take her on a walk.
(probably the most awesome reaction I got was the facepalm look on the face of a police officer wanting to fine me for not having my dog on a leash until he noticed it was a cat. There's no law mandating cats be leashed, contrary to dogs)
How the hell did she teach herself that? It's not the cat that used to walk with the dog. She never walked with me when I still had the dog, and used the litterbox. I never taught her to do her crap outside. It's awesome though, makes for lots of nice reactions from passers by.