Bubble Bath Pirates, by Jarrett J. Krosoczka, Viking, 2003.
I had forgotten about this book until I bought a copy for my five-year-old. NOW I remember it. We used this book at least once a year for story times at the library, and I remember the moms (not so much the dads) glaring at me when the kids had ice cream after their baths.
The reason we used it so often is because the book was fun to read out loud to a group of twenty or thirty preschoolers. It still is fun to read out loud to much-loved audience of one. And, now I'm the mom, so I get to tell my son that he needs to eat ice cream BEFORE his bath.