Grandpa Joe is the tritagonist of the novel Charlie and the Chocolate Factory and its 1971 and 2005 film adaptations. He is Charlie's paternal grandfather who accompanies his grandson to Willy Wonka's chocolate factory.
He is also stated in the book to be in his nineties; although both of the actors who played him were younger. And in the book he was described as bony, or resembling a skeleton. But in the 2005 film, Joe was not skeletal, but skinny. He went along with his grandson Charlie on the Wonka Tour.
In the 2005 film, Joe mentions to Charlie that he used to be an employee at Wonka's factory before Wonka had to close off the factory and lay off all its employees. When Joe and Wonka meet again, Wonka questions if he had been one of the spies, and when Joe replies that he never was one, Wonka welcomes him back.