Apparently if a three year old witnesses a Polly Pocket shoe vanish down the drain of the bathtub, it can scar her for at least a few weeks.

I personally didn’t think those little Polly shoes could get any more insidious. But thanks to one of them, Sid is boycotting the bath.
She saw that useless little shoe disappear into the plumbing underworld and now, the thought that she may follow suit has completely spooked her.
No baths for Sid.