AE3803, also known as Red Blood Cell, is the main protagonist of the anime series Hataraku Saibou (Cells at Work!). She is a cheerful and hardworking erythrocyte responsible for transporting oxygen and carbon dioxide throughout the body. Despite being clumsy and often getting lost, she is determined to do her job well and learns from her experiences. Her interactions with other cells, especially the White Blood Cell, provide insight into the workings of the human body and the importance of teamwork.