Simba's discovered that the two toilets in the house are great places to get water when he's feeling too lazy to walk over to the proper water bowl in the kitchen or use the water bottle in his crate.
One problem is that he's a really messy drinker, and ends up soaking the mats and dripping all over the place.
The other problem is that I usually put those Clorox toilet tabs in the tank to help keep things clean. Probably not too healthy for him to be drinking the water.
One more reason to remember to keep the lid down.