Mr. Pumblechook is Joe's uncle, but Mrs. Joe considers him to be one of her BFFs. He's the local seedsman (he sells seeds and stuff) and is charged with escorting Pip to Miss Havisham's house for the first time. Because of this, Mr. Pumblechook believes that he had a big hand in helping Pip to his fortune. He tells everyone he meets this, and Pip is thoroughly annoyed with him because, as he brags, Joe is silent.
He hoards food, he's greedy, and he likes to pour water into Pip's milk. Orlick eventually breaks into Mr. Pumblechook's house, ties him up, sticks flowers in his mouth, and robs him. We don't like Orlick, but we do think that Mr. Pumblechook deserves to be taken down a notch.