Very clever cat. He probably pees on their pile of laundry. 
I wouldn’t believe it without video.
I would.
Several decades ago when my roommate and I had cats we became aware of training techniques to teach kitty to use the human’s toilet. Our success was mixed, but it is possible to teach a cat to use a toilet. It would not surprise me to find a cat who had figure it out on his own.
Yeah, I can believe a cat using the toilet. No way am I going to believe that cat uses the toilet with out training. I call BS.
Maybe the family adopted the cat? Didn’t know its history.
The Cat thinks it’s cleverly trained humans to flush. 
Yeah, an untrained cat will drink from a toilet, but not crap in it.
pssssssssssssssssssssssssssssssssssssssst, it’s the cat.
I wonder if he leaves pee drips on the seat 
C’mon, he’s not an animal.
I have heard of people who have not only trained their cat to use a toilet, but also flush it when it’s done. So it is possible for a cat to learn how.
My husband spent months trying to teach ours. It did not go well.
So what is their son peeing into? The litter box?
My cats came with the potty using feature.
The breeder said, proudly, her babies are taught this when Mama Cat is teaching potty rules.
They do not flush.
I still have litter boxes. btw
It’s not as fun/smart/perfectly clean as some might think.
For my female it’s hit or miss. She gets all upset and makes a huge mess trying to cover her nasties with air. I’m usually alerted to this by my male Siamese howling the roof off. He don’t like his sister’s odor, I guess. I feel his pain.
I have caught him trying to fish his nasties out of the water. Washing his hands is fraught with pain coming from his claws.
So beware. YMMV
I hadn’t considered any downside to a toilet trained 
.
Thank you for contributing your experiences.
This is exactly how I picture it working! Nothing is that simple.
Well you can now. I had a cat that used the toilet to poop. She would not go near the litter box no matter what kind of litter we used. She would PEE on the floor or anything that happened to be on the floor but somehow she realized she could poop in the toilet I SWEAR ON MY MOTHER’S GRAVE nobody taught her how to do it. We had four cats at the time and this was the only one that did it too and she came to us as a young cat (not a kitten, probably about six months old). She wasn’t particularly smart either. She just … I dunno, liked the way it felt to poop in the toilet I guess.
She didn’t flush either.