The Thirsty Bulldog was first noticed in Melbourne Australia. It is a male ritual often performed by supporters after a footy match. It involves mooning the opposition fans, but the glans penis must be pushed back through the legs so it becomes wedged between the buttocks. In it's extreme form the "bulldogger" will urinate during the ritual, hence providing the slobbering metaphor of the Thirsty Bulldog.
Supporter Group 1 "You floggers got thrashed your team is shytte"
Supporter Group 2 "Hey look here we have captured you mother"
At this point Supporter Group 2 appoint themselve to the "Thirsty Bulldog" position.
Plonker at pub:- "I've tried so hard to crack onto Lynn tonight but she thinks I'm a drunken todger"
Mate of Plonker:- " Hey your too good for her son...let the thirsty bulldog off the leash so she can see what she is missing...she'll soon come grovelling back"
Yeah what a great idea
Plonker then unleashes the thirsty Bulldog.