Dr. Valentine Ruster is a Muppet doctor from the Barrio Sésamo mini-series, Monstruos Supersanos. He teaches his Sesame Street friends about doing things to keep the heart healthy, such as exercising and eating fruits and vegetables. He also hosts health-themed game shows.
His name is a play on Dr. Valentin Fuster, heart surgeon and founder of the International SHE Foundation. Dr. Ruster is made from the orange live-hand Anything Muppet pattern.