In the scene where Castle realizes "Sean Elt" is an anagram of "Stan Lee", and Beckett writes it on the murder board, during one take, Stana Katic wrote her own name instead. That take is featured in the DVD gag reel.
Stana Katic voiced comic book character Talia al Ghul in Batman: Arkham City and appeared in comic book movie The Spirit.
The comic book store owner is impressed to see a Hulk #181. This issue features the first story appearance of Wolverine, and if in excellent mint condition, is worth several thousand dollars.
When Castle asks Detective Beckett which super hero she would want to be, she chooses Elektra, a knife-wielding assassin. Stana Katic herself starred as a knife-wielding assassin in the 2008 film, Stiletto (2008).
The title of this episode is taken from the Beach Boys song, "Heroes and Villains."