工人階級

工 = 二 + 丨 : Mnemonic symbol: a steel beam, since 工 looks like the cross section of a steel beam. In front of the engine ((e)ng1), Gitta Giraffe (gu) is doing some hard work: She's stacking a capacitor (二) on a dinosaur bone (丨) on a capacitor (二). She's not very successful, but then she gets the idea to use steel beams (工) as support.

人 = 丿 + ㇏ : Mnemonic symbol: Neanderthal Man (人). Robinson Crusoe (r-) is looking for snacks in the encampment's kitchen (-en2) when he suddenly spots Neanderthal Man (人). Neanderthal Man offers him a banana (丿), but Robinson Crusoe doesn't trust the present and pokes it with a finger (㇏).

阶 = 介 + 阝 : The pope (阝) sentenced Joan of Arc (ji) to death and wants to shoot her to outer space using a rocket (介) in front of the elevator (e1). He doesn't have a proper launch ramp, so he just uses some stone stairs (阶).

级 = 及 + 纟 : Joan of Arc (ji) closely investigates her newly arrived troops just inside the space station's entrance (Ø2). She ranks (级) them according to their level (级): First there is a silk worm (纟) which can at least shapeshift. On the next level, there is Yuwen Huaji (及), who has no comparable super power.