We went to the Clark Planetarium today, and Henry came home with the planets of our solar system more or less memorized in order starting with Pluto* I guess he did spend a bunch of time running back and forth along the alley with the planets hanging and asking me the names, but I really wasn't expecting him to know all their names. *He knows it isn't a planet - the planetarium left their scale model of Pluto hanging, though, and replaced it's display sign with one about all the dwarf planets.