In my lifetime, there has always been nine planets. I know Pluto only came on board in 1930, and its maybe a bit small and fluffy to really be a planet, but I have always welcomed it into the fold. In illustrations of all the other stuff floating about orbiting the sun, only the Magic Nine are ever given that fat, round, planety look.
Now, its seems that "planet" is on the verge of being redefined. Soon we could have around 53 bodies in the planet category. Hats off to anyone who can write a good mnemonic for that list. Especially when some of them have names like "2003 UB313".