Not the toilet, but my last cat used to like to drink from full bathtubs. If you ran a bath and then left it for a few minutes, you'd find her on the edge having a drink. Once I came in and yelled her name, which startled her and she fell in the tub!
She also fell into a half-full fishtank once... It had a glass lid so when she jumped on top for the umpteenth time the lid cracked in half and in she went.
She also fell into a half-full fishtank once... It had a glass lid so when she jumped on top for the umpteenth time the lid cracked in half and in she went.