Friday, as I was putting the finishing touches on dinner, Laurel disappeared into her bathroom with an Ikea toy pot. I heard the water running, and figured she was filling her pot up with water, dumping it out, filling it up, dumping it out... When she closed the bathroom door and didn't emerge after a while, I ran to check on her. I opened the door, and she's in the process of pulling up her underpants. "Good job going potty by yourself, Laurel!"
And then I saw the pot on the floor. With urine in it.
Mercifully she didn't pee on the floor.
I think she got the idea from watching me clean out the car earlier in the day - she's fascinated by the travel potty I keep in the car "just in case".