when pigs fly

Once, there was a horse named Shelly whose only dream was to fly. But no matter how fast Shelly ran, she could never lift off the ground. Pinky the pig laughed at her, snorting "Horses can't fly!" Then, Shelly met a man who wore a very large hat. The man put a loop of rope around her, and took Shelly to a strange place where the ground was very hard and smooth. He put Shelly in a large metal container, which

rumbled and rumbled, and when Shelly looked out the window, she realized she was high, high up in the air. She was flying! She neighed in happiness, braying "Look at me now, Pinky! The next time you make fun of me will be when pigs fly!"

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something is very unlikely to happen; impossible

&

when hell freezes over

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french

à la Saint-Glinglin / on Saint Glinglin's day

spanish

cuando las vacas vuelen / when cows fly

german

wenn schweine fliegen können / when pigs fly

italian

no translation

arabic

"في المشمش” / when the apricots bloom

japanese

no translation