Bradley Whitford, who receives a "special guest star" credit, appears on screen for less than ten seconds and says just five words: "Dr.Greene" and "Yes he is"" .
Mr. Calus (which is misspelled in the credit listing, but spelled correctly in the subtitles) is an anagram for Mr. Claus.
Julianna Margulies (Carol Hathaway) & Michael Bryan French (Dr. MacGruder) also worked together on episode 4.9, A Defense of Marriage (2012), of The Good Wife (2009) as Alicia Florrick & Vance Foster respectively.