The Mona Lisa is a famous painting kept on display in the St. Canard Museum. Occasionally, someone aims to steal it.
The Mona Lisa, or at least its mouth, is voiced by Michael Greer.
The Mona Lisa is one of the most famous paintings in existence and as such worth a fortune. There might be two versions of it around, both of which are kept in the St. Canard Museum.
Inspired by her fence, Splatter Phoenix steals the mouth of the Mona Lisa to get ransom for. The mouth is not happy with this and does everything in its power to thwart her. When she jumps into a painting to escape, Honker follows her and the mouth saves him by biting Splatter in the back when she is about to attack him. Honker fails to take the mouth from Splatter, but he does reunite with Darkwing Duck, Launchpad, and Gosalyn. Before Splatter can sneak off, the mouth whistles for attention. A pursuit ensues during which Splatter paints a prison around the mouth when it keeps getting in her way. In the end, it is her own cartoon prop that defeats her and frees everyone. Honker finds the mouth stuck on his forehead just moments before his family, the Muddlefoots, arrives at the museum to find him, thinking him out and about with criminal intents. They interrogate him, so the mouth takes a stand for the boy, assuring his parents that he is an honest kid before returning to its proper place on the canvas of the Mona Lisa. During a robbery for a precious gemstone, Ample Grime takes a break to besmirch several paintings, among which the Mona Lisa.
Steelbeak, Tuskerninni, Moliarty, and Megavolt join forces to create the ultimate weapon: a giant Darkwing Duck robot. For this purpose, they steal the Mona Lisa, draw up the robot's design scheme on its back, and cut it up for the latter three to each have some of the design plans. Darkwing Duck goes after them and retrieves the pieces. By putting the Mona Lisa back together, he finds out about the robot.