Pluto

This evening I helped Alyssa make a solar system. So we've got a big, soft, yellow ball in the middle with nine smaller balls in orbit around it, fixed spoke-like by lengths of coat-hangers. It looks like a cross between an Alexander Calder mobile and a Philip Treacy hat gone wrong, perched precariously on top of a shadeless table lamp. It would have been great to have the bulb inside the sun but too much of a fire hazard.
Alyssa tells me that Pluto isn't a proper planet. It's a dwarf planet. It must be really disappointed. Imagine, floating around in space for billions of years and then someone invites you to join their club, which is really exclusive - just 8 members. You get a badge and subscription to the Solar System News and discounts on stuff and then, a micro-second later, you receive a letter saying it was all a mistake and having checked references you're not a planet after all so you can't join. 

Of course the best thing about Pluto is its name, proposed by an 11-year-old schoolgirl, Venetia Burney, from Oxford in 1930 (the year it was 'discovered'). Sadly it was not inspired by Disney's dog, created the same year, but the Roman God of the Underworld who was able to make himself invisible (which the planet - sorry, dwarf planet - managed to do very successfully up until then). So anyway, Venetia heard about this bogus new planet, suggested the name to her librarian grandfather, who passed it on to an astronomer friend, who telegraphed it to the Lowell Observatory in America, who said yes. 
Venetia lived to the rope old age of 90. Three years before she died, her beloved Pluto got de-planetized. Her view? "At my age, I've been largely indifferent to [the debate]; though I suppose I would prefer it to remain a planet". Me too.