Castlevania: Rondo of Blood is designed to be compatible with a Version 3.0 System Card (distinguished by the Super CD-ROM² branding instead of the CD-ROM² brand found in earlier versions). Despite this, if the player inserts a Version 1.0 or Version 2.0 System Card before bootup, the game will enter Akumajyo Dracula Peke, a hidden self-parody minigame. The title logo is deliberately misspelled (i.e. "Akumajyo" instead of "Akumajou") and written almost entirely in hirigana save for the "X" at the end, which sports furigana reading "ペケ" ("peke"); the latter is a Kansai dialect term for a wrong answer or prohibited action, riffing on the fact that the player inserted the wrong type of System Card. Upon pressing the Run button, the game will then load up "Stage X", featuring a much more cartoonish art style and a splash screen claiming that "The fated bloodline will fail without a Super CD-ROM²." Reaching the end of this stage results in Maria apologizing before text appears instructing the player to turn the game off and swap out the System Card for a Version 3.0 one.

Akumajyo Dracula Peke is retained in both Castlevania: The Dracula X Chronicles and Castlevania Requiem, complete with an English translation. However, the ending text is changed to accommodate the different methods used to unlock it in each re-release. In The Dracula X Chronicles (where it is unlocked by beating Boss Rush Normal three times, the third while having the Key sub-weapon during the Lesser Vampire fight), the text reads "Press START button to quit this game." Meanwhile, in Castlevania Requiem (where it is unlocked by inputting the Konami Code while highlighting "Options" in the main menu), it reads "Castlevania Requiem does not support extra lives codes. Press Options to quit, cheater." Both re-releases additionally rewrite the splash screen at the start of the level to say "Destiny cannot be stopped here."

There is a hidden audio track message warning the player to not play the disc in a audio CD player. The warning is a small skit between Richter and Maria. Though only in Japanese, it seems that Maria initially scares Richter and Maria then warns him to not put the disc into an audio CD player. Richter questions why she knows all this before seeing she's been reading off of a piece of paper. Richter then warns people to turn down their speakers as it may blow them out before the disc goes onto track 2. A similar audio track is present on the disc Castlevania: Symphony of the Night.

The intro stage is the same as the Town of Jova from Simon's Quest.

In Stage 5 of Castlevania: Rondo of Blood, there is a secret passageway that can only be accessed by Maria. It leads to a white object resembling a mirror or doorway that cannot be interacted with. In the PSP remake, a Soundtrack item can be found here.

The track "Requiem," which plays on the file select screen, is derived from Christian liturgy. The phrase being sung, "Kyrie eleison," is Greek for "Lord, have mercy."

There are unused sprites in the game's memory for a giant lizard-like creature which shoots a beam from its mouth.

In the Akumajo Dracula X CD liner notes, the game's character designer Toshiharu Furukawa stated that they had to remove some monsters in previous Castlevania games, due to the game's international localizations. Having destructible monsters with humanoid forms (i.e. Medusa, Carmilla, and Gargoyle) went against America's morals. However, for Castlevania: Rondo of Blood, it doesn't need to be localized, due to it being released in Japan-only.