The Tubs in your Sim's Bathrooms

@emorrill
Its not, its a known glitch.Lots of people have it, some don't.According to Igazor, for some reason when owning a large dog, it causes the bathtub to keep creating a route for the dog to get to the tub, in turn it slows the game down, causing sims to become idle blobs of nothing.XD

Edit: I qoute from Igazor(from a thread by another simmer with same issue)

But there is another possible explanation that came to light since this thread started. Some players who have large dogs in the household have reported that FW stops working for them for no reason. This is a game bug going back to when Pets was released that apparently never got fixed all the way, but the solution (strange though it sounds) is to replace all of the bathtubs in the house with showers and keep a tub in the family inventory only for when the dogs need a bath. Of course, if your sims don't have large dogs, none of this applies.

and

he issue involves any tub in which you can bathe a dog so the answer is yes it does include those if such is possible. Apparently the game keeps checking to see if there is enough space around the tubs to get the dog inside, like a thousand times a minute, even when the dog doesn't need a bath and uses up too many resources in the process. Or something like that.

I really thought this bug was solved by a patch long ago, but a few players have come to us with it resurfacing again.