If the game detects a pirated copy of the game, all enemies will be removed from the game except for those from the first level.

On the title screen, entering the Konami Code will play a short tone as if a cheat code was entered correctly, but pressing Start afterwards will instead send you to a black screen with the message "SORRY! NOTHING THIS TIME!". Based on existing coding for an additional cheat flag in the game's data, it's possible that this use of the Konami Code was originally meant to activate a different cheat that would grant 50 lives at the start of a new game, more in line with past uses of the Konami Code.

In the Famicom release and the Japanese version of the Game Boy port, the first boss' forehead bears a manji, a Buddhist symbol for balance representative of love, mercy, strength, and intelligence. However, outside of East Asia, the manji is widely seen as a hate symbol due to Nazi Germany appropriating a modified version of it as the swastika. Consequently, the international release of the Game Boy edition removes the icon; the top of the boss' head is also made rounder to further reduce visual similarities to a Ku Klux Klan member.

The Castlevania Anniversary Collection reissue of the Famicom version similarly removes the manji from the boss' design, but does not alter the shape of his head. This change is also present in all versions of Castlevania Anniversary Collection rather than being limited strictly to the international release.