In the book “Inside of a Dog,” Alexandra Horowitz theorized that dogs urinate on a rock or a tree in order to leave a message for other dogs. When Gizmo does that, he is revealing what time he was there (the latest odors will be the strongest), the state of his health, a little note about where he is emotionally and perhaps other messages which we have yet to decipher.
Personally, I believe that Gizmo is leaving love notes or sexual invitations, which might be translated something: “Healthy male dog seeking companionship of female who loves doing it doggie style. No wierdos, please.”
That leaves us with several questions, including the mystery of “air” whizzing, which is like air guitar (pretending or miming playing). Why go through the effort of raising his leg and then prancing triumphantly away when no yellow liquid is left behind? Is Gizmo leaving an “air” scent for the next dog?
“Air” whizzing absolutely requires that the quotes indicating irony surround the word. Does this mean that a dog somehow understands the concept of irony?
"If your dog is fat, you aren't getting enough exercise" -- Unknown