In turning a poem on its opposite pole, the parodist must be wary of exact opposites to the author's words. They don't always reverse the sense, and they can land you back in the original meaning. Just as two negatives make a positive, "what should appear" = "it can't stay hidden." Keep a copy of Clement Moore's "A Visit From St. Nicholas" next to you to keep track and compare.
"Moore or Less the Night Before Christmas,"
Word Ways: Vol. 29
, Article 4.
Available at: http://digitalcommons.butler.edu/wordways/vol29/iss4/4