用坏

用 = 丨 + 月 : Mnemonic symbol: a first aid kit. Can you see the cross on the container?

用 = 丨 + 月 : Yu the Great hurt her leg when she slipped in the engine's bathroom. The moon helps her to splint her leg using the bathroom's first aid kit and a dinosaur bone.

坏 = 不 + 土 : In the airplane's bathroom, there is a clear sign that it is forbidden to enter the room with dirty feet. Helga Horse is quite spoiled though, so she enters right after she went to the muddy stables and spreads dirt all around.