Because the teacher said it was a piece of cake!
or
He made an illegal ewe turn.
or
100: One to do it and ninety-nine to say "I could've done that."
or
What's the use, they'd still have bear feet
or
When it came time to pay, the skunk didn't have a scent, the deer didn't have a buck so they put the meal on the duck's bill.
or