It's actually really easy to get five of the planets and the days of the week in Japanese all in one shot as long as you know the Latin roots for these.

To demonstrate, in French and Engilsh the days of the week are
lundi, mardi, mercredi, juedi, vendredi, saturday (EN), dimanche

The planets in English:
(__, Mars, Mercury, Jupiter, Venus, Saturn, __)

and in Japanese, the planets:
(__, 火星, 水星, 木星, 金星, 土星, __)

and the days:
火曜日, 水曜日, 木曜日, 金曜日, 土曜日

I should admit though, that while these help with remembering the connection between these two sets of words in Japanese, recalling this relation probably isn't the best way to learn them unless you know the Latin roots and one of the word sets well enough to use as a basis.

~~~~