What made Back at the Library brilliant to me is this.
Uncle Grandpa is some sort of ageless immortal, as are the rest of his crew. They easily could have written the episode so his tardy library book was hundreds or thousands of years late and racks up millions of bucks as a fine. But they went with UG overreacting to a week late's fine of 12 cents. They went with the less obvious Uncle Grandpa scenario, and the episode was all the funnier for it.
Uncle Grandpa is some sort of ageless immortal, as are the rest of his crew. They easily could have written the episode so his tardy library book was hundreds or thousands of years late and racks up millions of bucks as a fine. But they went with UG overreacting to a week late's fine of 12 cents. They went with the less obvious Uncle Grandpa scenario, and the episode was all the funnier for it.