The fish hold a race to choose a king, and the sole, jealous at losing to the humble herring, ends up with her mouth twisted to one side forever. A tiny, tidy origin story about envy, quick enough for a single breath before lights out.
From Grimms' Household Tales. See the whole collection.
The fishes had for a long time been discontented because no order prevailed in their kingdom. None of them turned aside for the others, but all swam to the right or the left as they fancied, or darted between those who wanted to stay together, or got into their way; and a strong one gave a weak one a blow with its tail, which drove it away, or else swallowed it up without more ado. “How delightful it would be,” said they, “if we had a king who enforced law and justice among us!” and they met together to choose for their ruler, the one who could cleave through the water most quickly, and give help to the weak ones.
They placed themselves in rank and file by the shore, and the pike gave the signal with his tail, on which they all started. Like an arrow, the pike darted away, and with him the herring, the gudgeon, the perch, the carp, and all the rest of them. Even the sole swam with them, and hoped to reach the winning-place. All at once, the cry was heard, “The herring is first!” “Who is first?” screamed angrily the flat envious sole, who had been left far behind, “who is first?” “The herring! The herring,” was the answer. “The naked herring?” cried the jealous creature, “the naked herring?” Since that time the sole’s mouth has been at one side for a punishment.
Public domain. Text from Grimms' Household Tales (Margaret Hunt translation, 1884), via Project Gutenberg. View the source edition