Why does absurdity beat realism for memory images?

The brain filters out the ordinary and expected; the bizarre and surprising survive precisely because they violate expectation.

You forget the thousandth ordinary coffee cup, but you'd never forget a coffee cup the size of a car pouring lava over your keyboard. Memory is tuned to notice the unusual — it's information-rich and potentially important. Deliberately breaking realism (impossible scale, impossible behaviour, absurd juxtaposition) is therefore a feature, not silliness: it's how you make an image the brain refuses to discard.