We used Joseph's 9-and-three-quarters birthday as an excuse to throw a Harry Potter party! By "party," I mean just the three of us, cake, balloons and a bunch of free printables. We're on our second run through the series on Audible, and I made a big fuss about this 9-and-three-quarters birthday to encourage a love of reading and fractions. (Always the ulterior motive.)
My story is on Seattle's Child here.