Patricia Thompson, commonly called Patty, is a demon weapon in the anime Soul Eater and the younger sister of Elizabeth Thompson, also known as Liz. Together, the two sisters form the twin pistol weapon set wielded by the meister Death the Kid. Patty is the younger of the two sisters. Before becoming Death the Kid's weapon, she and Liz grew up on the streets of Brooklyn, New York, where the two lived in poverty and resorted to petty crime, earning the pair the nickname the Brooklyn Devils. They were eventually found and taken in by Death the Kid, who became their partner.

Patty has a distinctly childlike and innocent personality. She tends to view nearly everything as a game, speaks in a sing-song cadence, and often mispronounces words in a way that resembles a small child, such as saying hullo for hello and sowwy for sorry. Her behavior is frequently bizarre and unpredictable, and she can come across as airheaded or simple-minded. For example, during a written examination, she uses her test paper for arts and crafts instead of answering the questions. She also throws tantrums when things do not go her way, such as becoming upset when overheated in the desert. Despite her carefree demeanor, she is not lacking in warmth, and she does cheer up Death the Kid when he becomes frustrated with himself.

Her primary motivation is to have fun and enjoy herself, and she approaches her duties with the same playful attitude she applies to everything else. She is loyal to her sister and to Death the Kid and supports them in their mission as part of a meister weapon team. In battle, she tends to rely on cooperative tactics with Liz and Kid rather than independent strategy, and her naivety can limit her ability to plan under pressure.

Within the story, Patty serves as the junior half of Death the Kid's dual weapon team. She and Liz transform into a pair of pistols that Kid wields in combat, and their weapon form allows them to collect the souls of defeated enemies in their magazines, a unique trait of their abilities. When Kid is not present, Patty is able to use Liz's weapon form and Liz can use Patty's, allowing the sisters to operate with another wielder if needed. Her combat potential is strongest when paired with Liz and channeled through Death the Kid, who amplifies the power of their attacks.

Her most important relationship is with her sister Liz, with whom she shares a deep bond and relies on heavily in battle. The dynamic between Patty, Liz, and Death the Kid is defined by contrast: Patty provides comic relief with her lighthearted and playful outlook, while Kid is serious and obsessively concerned with symmetry. Patty enjoys the drama created by Kid's perfectionist tendencies, and her cheerful responses to his frustrations are a recurring source of humor in the series. At the same time, she is supportive of him when he becomes down on himself.

Over the course of the series, Patty's character develops as she is exposed to increasingly serious conflicts. Although she is initially presented as someone who does not take anything seriously, her experiences during major battles, including confrontations with the Arachnophobia organization, begin to show her the real stakes involved in being a demon weapon and collecting souls. These moments contrast her innocence with the gravity of the situations around her and mark her gradual understanding of the dangers and responsibilities of her role.