Grandpa George is Charlie’s maternal grandfather (paternal in the 1971 and 2005 films). He is married to Grandma Georgina. He is played by Ernest Ziegler in the 1971 film and David Morris in the 2005 film.
Grandpa George was a minor character in the first book and didn't have much to say or do; it wasn't until the sequel, Charlie and the Great Glass Elevator, that his character was developed more. In this case, he was somewhat grumpy and questioned Wonka frequently.
He was in the 1971 film, where again he was a minor character and had very few lines. In the 2005 film he was a lot more developed; he was more cynical and stubborn, and had a tendency to go into rants.