Toddlers with max Potty skill can click on a Potty and gloat about their dominion over it.
Latest: V4, released after EA Patch, November 12, 2019
Once your Toddler has max Potty skill, a new interaction will be available on the Potty called Potty Gloat. Upon using the interaction, your Toddler will do a little dance for a bit, in front of the Potty, demonstrating their superior motor function. At the end of it, they get a one hour moodlet, which varies depending on what Toddler trait they have.
Some ideas don't have a logical origin. I made this as a fun little side project for giggles. At the time, I was imagining what might be a cute little extra interaction, something small in scope, for Toddlers and came up with this idea.