 http://www.singaporeenglish.com/shortstory2.html:

", my son, why do you walk sideways like that your toes turned ? " Mother Crab said as she neared young crab. 
young crab puzzled. He said, "But mama, I always walk sideways my toes turned . Papa you also walk sideways your toes turned . " 

"No, no, no. That not correct way. You should always walk straight forward your toes turned , " said Mother Crab. 
So, obedient young crab tried do as he told. But try as he might, he couldn’t. end, he said, "Mama, I can’t walk straight forward my toes turned . Can you please show me? " 

Mother Crab very glad hear that her son willing learn. "I will show you, my son. Now step back watch carefully, " said Mother Crab. 

that, Mother Crab stretched one her legs, turned her toes tried take step forward. But as soon as she did that, she tripped fell flat her nose!