They both have trunks
or
Because there's no one else to wag it for him.
or
Because he never pays his debts.
or
A river.
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
or
None. Bill Gates will just redefine Darkness® as the industry standard.
or