The fishing cabin where the judge receives his chemotherapy treatments is the same cabin that was used in Divine Secrets of the Ya-Ya Sisterhood (2002) (where Siddalee stays after fighting with her mother). Both movies were filmed in Wilmington, NC.
There are three additional references to previous roles Robert Duvall has played: 1) The bailiff's name is Augustus or Gus....Duvall has often said that the role of Augustus McCrae in Lonesome Dove (1989) was one of his favorites. There's a bit of a gleam and a subtle smile when Duvall's character says "Gus". 2) When Sam and Hank are discussing their past at the lake, Sam uses the phrase "A more superior prick never shit between two shoes". Duvall's character in The Great Santini (1979) is described as "The greatest marine fighter pilot that ever crapped between two shoes!" 3) Sam talks about "an offer he can't refuse," a line from The Godfather (1972) where Robert Duvall played Tom Hagen.
Both Judge Palmer, and his doctor, tell Hank Palmer that Judge Palmer has been undergoing chemotherapy for a year. In court, Judge Palmer states that he has been undergoing chemotherapy for six months. In a real trial, Hank Palmer - as a defense attorney - would have been obligated to correct Judge Palmer's deliberate effort to diminish the extent of his treatment, but Hank Palmer does not do that.
Judge Palmer mentions that Hank's (Robert Downey Jr) wife was "playing hide the pickle". In 'Avengers 2: Age of Ultron', Tony Stark (also played by Downey) says that Black Widow and Bruce Banner are "playing hide the zucchini".
The name Hank Palmer combines two heroes from Marvel and DC comics: Hank Pym and Ray Palmer, and both of them are size shifters and are scientists. Robert Downey Jr. who plays Hank Palmer, has also played Tony Stark, a Marvel comics scientist, in Iron Man (2008) and succeeding movies.