Poopie has sent a meme to me: Turd in a punch bowl are the 1st and 3rd lines, you make up the 2nd and 4th lines and they have to rhyme.

Ahem:

Turd in a punch bowl
Better than the tub?
Turd in a punch bowl
Rub a dub dub.

(and yes, last night my charming Princess Fiona shouted to me from the bathtub, she was standing on her tippy toes and pointed into the water where she had created quite the masterpiece)