A tale from Kunigami, Okinawa Island, Japan, tells a story of how frog and crab were having a race. They were agreed to mount each other’s back while the other run. The first runner was the Crab. With the frog on his back, he ran really fast.
When the frog turned to run, he was jumping into the night sky with the crab on his bag. The crab was awed, but soon replaced with anger when he finally getting down the frog’s back. They were still in the same spot where the crab had stopped.
The frog was actually only jumping in one spot. The furious crab then clamped the frog’s waist, making it bent.
Source:
Crabs Folklore 