Stan tells Peggy that his cousin, Robbie, has been killed in action in Vietnam. This is the same cousin who came with Stan to Don's 40th birthday surprise party.
Dr. Shelly Hecht was based on real life Dr. Max Jacobson, who lost his medical license in 1975 after a patient of his died from intravenous amphetamine poisoning.
The episode's title Crash has a double meaning. It started out with a literal car crash, and to crash out on speed, which Don (and the office) was injected with.
The coins that Wendy throws are for I Ching (or Yijing), an ancient Chinese hexagonal oracle-like system.
Final televised appearance of Alexa Nikolas before ending her acting career.