The Fat Man is a portable nuclear catapult with a distinctive, bulky design, featuring a large, curved launch tube mounted on a sturdy, angular frame. The weapon's surface is heavily weathered, with visible rust, scratches, and peeling paint, reflecting its post-apocalyptic origins. The launch mechanism includes a detailed, mechanical loading system and a prominent pressure gauge, while the overall color scheme is a mix of dull metallic grays and faded military greens, accented by worn yellow hazard stripes.