Because there's no one else to wag it for him.
or
Because he saw the salad dressing!
or
Address.
or
Three skunks fighting over a pickle
First dog: My master calls me Furball. How about you?
Second Dog: My master calls me Sitboy
or
Does it have to be a light bulb? I've got this neat candle holder...
or
Can I have your hand, hand, hand, hand, hand, hand, hand, hand in marriage?
or