General silliness:
* The Porcelain Throne
* The Loo
* The John
* The Powder Room (especially if it's fancy)
* The Little Boys' Room (even if it's not)
* The Facilities (a bit formal, but still funny)
* The Restroom (always makes me think of a funeral home)
* The Can
A bit more rude:
* The Crapper
* The Bog
* The Head
* The Privy
More creative:
* The Throne Room
* The Sanctum of Serenity
* The Oasis of Relaxation
* The Temple of Hygiene
* The Land of Whispering Water
Remember, the best word for a bathroom is the one that makes you laugh!
Please be mindful of your audience and the context when using these words. Some might be considered offensive or inappropriate depending on the situation.