Instead of looking easy information up myself, I thought I would ask you all why it looks like dogs have four testicles. Might make a good discussion.
I would suggest you are either crosseyed, walleyed, or have been struck upon the head, as your perception is the minority.
only time i ever saw a dog that looked like it might ha 4 balls is when my male dog moochie had his knot swell inside the sheath and his balls had drawn up tight * his ball sack goes up and down depending on the temp* lol
http://en.wikipedia.org/wiki/Bulbus_glandis
The way a lot of furry artists draw the knot makes it look like such, but no, they don't.