In the backseat of a vehicle, a Jack Russell Terrier notices another dog pull alongside in a convertible. The other dog, an Afghan, is clearly female because its female owner is posh with long hair and the Afghan also has long, flowing hair.
Trying to impress the Afghan, the Terrier does all sorts of tricks, including juggling. While this is going on, the other vehicle leaves and is replaced by a black truck, this time with a bulldog in a spiked collar, whom we understand is male.
When the Terrier looks to see the results of his efforts, the bulldog winks... to which the Terrier makes an uncomfortable sound.
The ad could have played the same joke out with any change -- the car and Afghan were gone, another female dog or person is now watching, etc. -- and instead chooses a male dog (or is it a "Bulldog dyke"?) for a homophobic laugh.