That ep with the trip to Australia. They go there to make amends after Bart tricks an aussie kid into accepting a collect call from the US, lasting several hours.

This is the toilet at the US embassy, engineered to swirl the right way so that US personnel there don't get homesick, nodding to earlier in the episode when Lisa makes the claim to Bart about the swirl being the other direction on the southern hemisphere, which caused Bart to make that collect call to begin with.

Yes, I have in fact played knifeyspooney before.