Two neighbors had been fighting each other for
nigh on four decades. Bob buys a Great Dane and
teaches it to use the bathroom in Bill's yard.
For one whole year Bill ignores the dog. 

So Bob then buys a cow and teaches it to use the
bathroom in Bill's yard. After about a year and a
half of Bob's cow crapping in Bill's yard; being
ignored all the while, a semi pulls up in front
of Bill's house. 

Bob runs over and demands to know what's in the
18-wheeler. 
'My new pet elephant,' Bill replies solemly.