Dorapen, also known as the Mysterious Thief Dorapan, is a character from the Doraemons franchise, a series of spin-off stories featuring the cat robot Doraemon and his friends from around the world. Dorapen is a French robotic cat who operates as a gentleman thief, a character modeled after the famous fictional thief Arsène Lupin. Despite his chosen profession, he adheres to a strict moral code inspired by Robin Hood; his primary motivation is to steal from the wealthy and corrupt to provide for the poor and needy, and he never acts for his own personal gain. Consequently, he is often misunderstood as a common villain, but he carries his own loyal sense of justice.

In his personal life, Dorapen is constantly on the run from the French National Police due to his activities. He has a romantic relationship with a supportive girlfriend named Mimimi, who sees the best in him and trusts him with a powerful magical orb that is central to his operations. His favorite food is dorayaki, but unlike the traditional version, he prefers his filled with Camembert cheese instead of red bean paste. He also has notable phobias, including a fear of dogs, known as cynophobia, and a fear of dark places, known as nyctophobia; however, he seems to be comfortable with robotic canines.

Dorapen possesses a variety of skills befitting a master thief, including mastery of disguise, deception, camouflage, and sleight of hand. His most notable ability comes from a distinctive wand or orb that is crowned with a jewel; this object grants him the power of transmutation, allowing him to change the form or properties of objects and even people. He also owns a cape that can transform into wings, enabling him to fly.

Dorapen plays a significant role as both an antagonist and eventual ally to the Doraemons. In his first appearance, he is forced to confront the group to steal their Friendship Telecard. However, it is revealed that he was being blackmailed by the villainous Dr. Achimoff, who had kidnapped Mimimi and fitted her with a deadly collar controlled by a button in Achimoff's golden tooth. Under this duress, Dorapen uses his disguise and transmutation abilities to temporarily defeat several members of the Doraemons. This forced antagonism continues until the deception is uncovered, at which point Dorapen uses a special card to destroy Achimoff's control mechanism, freeing Mimimi and siding with the Doraemons to defeat their common enemy. After the issue is resolved and the truth is brought to light, he becomes friends with the group, though he is ultimately forced to flee to avoid being arrested by the police who arrive on the scene. His character thus develops from a mysterious, misunderstood figure into a heroic ally and a recurring friend to the Doraemons, continuing his altruistic thievery independently.