A woman I met at the Carle Museum told me that there was precedent for censorious fiddling with Goodnight Moon, set by Ursula Nordstrom herself. I confirmed this hot tip in Leonard Marcus's Margaret Wise Brown: Awakened by the Moon:
"On Nordstrom's instructions, the udder of the Cow Jumping Over the Moon was reduced to an anatomical blur so as not to disarrange the fragile sensibilities of some librarians--the 'Important Ladies,' as she called them."
But, alas, at least one "important lady" was not to be budged--and the Horn Book Magazine never did review Goodnight Moon! It's kind of sad that Miss Nordstrom did not give us (librarians) more credit, though.