Planetary mnemonic

Planetary mnemonic is a way to remember something by linking it to something else. For example, if you wanted to remember the planets in order, you could use the phrase My Very Educated Mother Just Served Us Nine Pizzas. Each letter in the phrase stands for one of the planets, starting with Mercury and ending with Pluto:
M - Mercury
V - Venus
E - Earth
M - Mars
J - Jupiter
S - Saturn
U - Uranus
N - Neptune
P - Pluto
So if you wanted to remember the order of the planets, all you have to do is remember this phrase, and you'll remember their order!