国外内

国 = 囗 + 玉 : Mnemonic symbol: a nation's flag. Let's say the Chinese flag.

In the observatory's kitchen (o2) Gitta Giraffe (gu) is practising her ballet performance. She got a whole crate (囗) full of jade bracelets (玉) and flags (国) and fixed one flag to each jade bracelet. This makes a perfect combination for throwing the ring with the flag waving behind it and catching the ring again after a few pirouettes.

外 = 夕 + 卜 : There's a hole in the wall of the airplane's bathroom (ai4), and from outside (外), a bat (夕) wants to enter. Willy Walrus (w) is very afraid of bats, so he does his best to hinder the bat from entering with a voodoo staff (卜).

内 = ⺆ + 人 : Mnemonic symbol: A CT scanner to see inside of someone.

内 = ⺆ + 人 : Napoleon just can't find his stapler and suspects that Neanderthal Man has eaten it. Not thinking twice he orders Neanderthal Man to enter his CT scanner in the Eiffel Tower's bathroom, finding his stapler in Neanderthal Man's stomach.