Very interesting to explore english idioms. Please share your experience:) I know few, for example "Slip like a log" (it's about me) :))
If are very tired, you go 'out like a light'. You lay your head on your pillow and the next moment you are asleep, as quickly as if you had switched off a light. One moment it's on, and the next moment it's off. Out like a light.
It's better to explain what does this idioms means:)
and the pigs can fly.....