Seven Impossible Things Before Breakfast.
And the really good news is that Jeffers' next book, Up and Down is going to be another boy and penguin story.
Also, want to report that Jeffers is (as I suspected) one of the good guys. My younger son sent him a note and he wrote back. This puts him in the company of Mo Willems, Philip Ardagh, and Daniel Handler in my registry of writers who know how to treat their young fans. Okay, so Handler was writing to me and I'm not - technically - young. Still you know what I mean.