一去不復返

Maud Younger (y) forgot her keys to the space station (Ø1), all she brought outside was her flute (一). She has no choice but to crash the door with the giant flute.

去 = 厶 + 土 : Mnemonic symbol: The "nose" part (厶) can be seen as an arm, which goes through "earth" (土), and this reminds me of some protesters who lock themselves (or their arms, to be specific) to concrete barrels. Cupids dirt capsule could also be a concrete barrel. So in other characters, I'm going to represent 去 by a concrete barrel.

Cupid (qu) is trying to send himself to earth. In the bathroom of the space station (Ø4), he has prepared a capsule made of dirt (土). He's wearing his lucky fake nose (厶) when entering the capsule.

不 = 丆 + 卜 : Bruno Bear (bu) is setting up a wind wheel (丆) with a voodoo staff (卜) in the space station's bathroom (Ø4). He also puts a "forbidden" sign (mnemonic symbol for 不) on it, to make clear that it may not (不) be stopped.

复 = 𠂉 + 日 + 夂 : Mnemonic symbol: a photocopier.

Frieda Fox (fu) and the sun (日) have to wear high heels (夂) in the space station's bathroom (Ø4). The high heels are locked, and they only have one key (𠂉). They know that the key is very fragile and can only be used once, so they use a photocopier (复) to create more keys so that both of them can be freed.

復 = 复 + 彳 : Mnemonic symbol: a shrine of rejuvenation.

Frieda Fox (fu) only has an old photocopy (复) of her favorite black sneaker (彳). She restores (復) her sneakers to the original state by putting the old photocopy into the shrine of rejuvenation (復) in the space station's bathroom (Ø4).

返 = 反 + 辶 : The protester (反) just entered the anthill (an3) wearing socks and gladiator sandals (辶). Frankenstein's Monster (f) protests loudly and tells the protester to go back (返) where he came from to either wear sandals and no socks, or socks and proper shoes.