10 Best Family Guy Characters Only In One Episode

Stewie has seen his fair share of enemies over the course of the show, that much is certain - but none more ruthless, uncompromising and woefully unexplored than Penelope.

Voiced by Cate Blanchett, Penelope makes her appearance in the episode, "Mr. and Mrs. Stewie", at the park where Stewie is playing. They are found to have a lot in common, and Stewie quickly becomes infatuated with her.

However, Penelope has a kind of terrifying resolve that Stewie lacks, revealing that she actually managed to murder her mother (much like Stewie's recurring threats and/or attempts to kill Lois), and teases out his evil side as they wreak havoc all over the world. When Brian intervenes, Penelope asks Stewie to prove his love for her by doing one last thing: killing his best friend.

When he refuses, she sets out to do it herself, culminating in an epic battle between the two destructive infants on top of a moving lorry. Stewie comes out on top, and, agreeing to stop her pursuit of Brian, Penelope kisses Stewie farewell before anchoring him to a lamppost and riding off into the distance.

It's a poetic departure for the character, and the writers must have thought so too, since she's never been seen again. But something about her deviousness and the influence she had on Stewie makes us think that Penelope still had a lot to give. A shame it may never come to fruition.