Cats certainly are crafty little creatures

[Figarosmom]

10. I had a cat that used the toilet.

He was so big he had a hard time using the box, he would sit on the edge and it would flip over on him. We didn't teach him, he figured it out. Must have watched us and figured he could do that.

We found out about it when my daughter's boyfriend was at the house alone sitting in the living room doing homework from college, when he heard the tinkle in the bathroom. So he went and looked and there was Dinkie, the cat sitting on the toilet tinkling away with his eyes closed. He still pooped in his box but he always used the toilet to pee.

Your cat likely watched you do it and figured it out from example.