孤
=
孑
+
瓜
:
Gitta Giraffe (gu) is currently the space station's lone (孤) inhabitant. To feel less lonely (孤), she drew a mosquito's (孑) face on a melon (瓜) to have somebody to talk to in front of the space station (Ø1).
独
=
犭
+
虫
:
Everyone has left the space station, only the animals are left: Doggy Dog (du), the dachshund (犭) and the mosquito (虫). They have noone who throws them a stick or exposes their bare body parts to bite. All alone (独), they wait in the space station's entrance (Ø2).
(of time or place) in; at; on / (indicating any indirect relation) to; toward; vis-à-vis; with regard to; for / (indicating a source) from; out of / (used in comparison) than / (used in the passive voice) by
于
=
亅
+
二
:
Mnemonic symbol: prepositions (in, at, on, to, ...) are what glue the sentence together. Honey is as sticky as glue, so I'll represent 于 by a honey jar.
Yu the Great (于) was assigned to repair the electronics of the space station's kitchen (Ø2), but instead he was snacking honey from a honey jar (于). Unfortunately his capacitor (二) got stuck in the honey and now he has to use a crowbar (亅) to lever it out.
Sherlock Holmes (sh) is cleaning a flower pot (廿) under the shower of the space station's bathroom (Ø4) with a loofah (L) because he didn't quite understand a poster next to the shower from the WHO (世) explaining dangers arising from different germs.