When Castle goes to visit Beckett in the hospital with his bouquet of flowers, Captain Montgomery's mysterious friend Mr. Smith surreptitiously passes by him dressed as a doctor.
This is the first time Detective Kate Beckett's age is mentioned; at the time she is shot, she's 31.
First time Castle and Beckett visit a swing set, which later becomes a recurring theme during the series.
Text on Castle's murder board:
Kate BECKETT: WHO HIRED THE SNIPER?
Johanna BECKETT: Was working on Pulgatti's appeal when she was murdered. Fatally stabbed by Dick Coonan. 3 colleagues also murdered by Coonan. WHO HIRED COONAN?
Joe PULGATTI: Mob source arrested by Raglan, who pinned Armen's murder on him
Bob ARMEN: Undercover Fed inside Mafia, killed 19 years ago in failed kidnapping attempt
Hal LOCKWOOD: Hired assassin, killed Raglan + McCallister. Part of continuing mission. WHO HIRED HIM?
3 Renegade Cops, All involved in Armen Homicide
Roy MONTGOMERY: Killed Lockwood and killed by Lockwood. What did he know about who hired Coonan + Lockwood?
Gary McCALLISTER: Shanked in prison by Lockwood (part of escape plan)
John RAGLAN: Killed by hired sniper Lockwood. WHO ORDERED THE HIT? Lead investigator in Beckett homicide, dismissed case as random violence
In Redemption II (1991), Data was told that Klingons would not be good therapists. Ironically, Michael Dorn who portrayed the Klingon Worf, portrays Beckett's therapist.