- Celebrity Voice Actor: The main cast of the series are voiced by well-known live-action actors, including Richard Armitage as Trevor and Graham McTavish as Dracula. Season 3 adds even more with Jason Isaacs and Bill Nighy.
- Fan Nickname:
- The leader of Dracula's demonic forces in Season 1 was given the name "Blue Fangs", since he doesn't have a name in the show, and because he stands out because of his glowing teeth.
- Alucard is often referred to as "Floating Vampire Jesus" after Trevor told Sypha "Tell it to your floating vampire Jesus here" in the midst of their duel.
- The Other Darrin:
- Ryotaro Okiayu, the Japanese voice actor of Alucard in the games since Symphony of the Night, is present as the voice of Trevor in the Japanese dub of the show. Instead, Shin-ichiro Miki takes over as Alucard, likely to avoid a case of Talking to Himself. Coincidentally, Miki has previously voiced Trevor's descendant Richter in the Japanese-only radio drama, Nocturne of Recollection, acting as a direct sequel to Symphony of the Night.
- In the Latin American Spanish dub, Lenore was voiced by Andrea Arruti in the first three episodes. Due to her sudden death, she is replaced with María José Moreno instead.
- Playing Against Type:
- Before this series, Frederator Studios was better known for producing cartoons aimed at children whose art styles were usually quite simplistic. This is in spite of the series and shorts produced for Cartoon Hangover containing content not suitable for kids. Even Adventure Time went into more darker territory and explored more mature themes as it progressed, which is why it became just as popular with adults despite being aimed at kids. Still, none of those series were ever as dark and graphic as Castlevania.
- Warren Ellis writes a story where God Is Good, religious artifacts actually stop the forces of evil, and while Corrupt Church is very much in evidence there are also definitely decent priests out there. Huh.
- Jason Isaacs in Season 3, as the cool, calm, pleasant, knowledgeable, yet forceful and determined Reasonable Authority Figure in the town Trevor and Sypha's story centers on. Subverted when it's revealed the Judge is, in fact, a prolific Serial Killer who targets the town's children, specifically those who (in his view) disrupt its peace and tranquility.
- Real-Life Relative: In the Latin American Spanish dub, Saint Germain and Hector's voice actors (Jose Luis and Alejandro Orozco respectively), are father and son in real life.
- Saved from Development Hell: This series was originally planned as a Direct-to-Video animated movie trilogy as far back as 2007.
- What Could Have Been: The series was originally going to be an animated movie trilogy.
- Word of Gay: Samuel Deats confirmed on Twitter that Alucard is indeed bisexual, following the sex scene between him, Sumi and Taka in season 3.
- Word of God: Animators for the show have frequently posted online to confirm which scenes or portions of scenes they animated, as well as who did what other portions. This is very helpful to the people whose interest is figuring out what animator animated a particular scene.
- You Sound Familiar:
Trivia / Castlevania (2017)