The grumbellies was a TV commercial in the U.S. for a fast-food restaurant that was bragging that it was open later than other stores. It might have been Burger King or Wendy's and circa 1981-1982. It was a cartoon-like comical voice inside someone's stomach making mumbling noises late-night. The person would then go out to the fast food place and satisfy his grumbelly. In one of the commercials the grumbelly said 'thank you' after the person ate the meal. I haven't seen the commercial yet on sites like youtube.
