Let me preface this by saying we do not use potty humor in our house. At all. Ever. Bodily functions are entirely off limits when it comes to jokes, and I can honestly say my kids have never heard us make any scatological jokes. (I have been known to sing about poop, but that's only while changing diapers. I've got to stay sane somehow.)
My two-and-a-half year old son, Dojo, likes to play with language. He thinks it's funny to choose a song or poem and insert a sound into every word--for example, singing Twinkle Twinkle Little Star, but ending each word with the letter K. "Twinklek Twinklek Littlek Stark! Howk Ik wonderk whak youk arek." So on and so forth. He thinks it's hilarious. I think it's amazing that at such a young age he's playing with words and sounds.
The other day he and Nayna were running around with laundry baskets on their heads, pretending to be robots (R2-D2 and the robot from Yo Gabba Gabba). "Nayna," Dojo said, "You're--R-Poop D-Poop!" He busted up laughing and looked at me with his patented I can get away with anything grin. "But we only go poopy on the toilet, huh Mama?"
My son invented potty humor.
Heaven help me.