In Joe's Revenge, Quagmire introduces Principessa as his new replacement for James. He asked Lois to watch over her, while he and the guys went off to go after a criminal. Brian gets jealous, when he sees Principessa kneading on a sleeping Lois' boobs and takes her place, landing himself in some real hot water, giving Brian a nonsensical hatred for her.
In Sex and The Kitty, Vinny fucked her, much to the anger of Quagmire. Vinny explained that it wasn't all that bad, given how promiscuous Quags himself is and how he's technically 1/16th cat, so it wasn't so bad. There was also a lit of debate over interspecies sex, which as we all know, was a metaphor for the debate about interracial marriage. Vinny explained the Italian etymology behind "Principessa" and said he's kind of made himself a prince. 9 cat months later, Principessa gave birth to a litter of Italian cat-dogs. They were all a bunch of cat-dog combos with tan or white fur, that all went "Ayyy!" all the time. Quagmire forgave him for this, because he thought they were kinda cute. Due to the events of Christmas Guy, this must have been erased from history.
In Roads to Vegas, Brian used his gambling winnings to hire a hitman to kill Principessa. Clones of Brian and Stewie would die later, and in the line for entry to heaven, Brian had an awkward encounter with Principessa, who angrily said "Hey." to him, in a realistic female voice. This is the only time Principessas ever talked.
- "Principessa" is Italian for "Princess".