Castle includes LGBTQ+ characters in incidental roles throughout its run, featuring them as victims, suspects, and supporting figures. Their identities are treated respectfully, and same-sex relationships are depicted without sensationalism or judgment. The show normalizes their presence within the narrative, neither actively uplifting nor denigrating queer identities.

The show 'Castle' features a transgender character, Chelsea, in the episode 'TransAction.' She is portrayed with dignity, complexity, and agency, navigating her career and family relationships. The narrative frames the prejudice she encounters as external societal issues. The main characters, Castle and Beckett, demonstrate a learning curve, evolving from initial unfamiliarity to understanding and empathy. This results in a net positive and affirming depiction of transgender identity.

The show portrays Christianity, particularly Catholicism through character Kevin Ryan, with respect, depicting his faith as a source of moral guidance and comfort. While individual religious figures may be involved in crimes, the narrative consistently distinguishes these as personal failings rather than an indictment of the faith itself.