Because 7 ate 9.
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
The same as a regular year, but with less calories.
or
If one side has one, the other side has to get one. Once launched, they cannot be recalled. When they land, they screw up everything forever.
or
First he lies on one side, then he lies on the other.
or