One obtainable item that debuted in this game and recurred in subsequent games is the Stone Mask, which is described in-game as being used in Aztec rituals.

This is a reference to the manga JoJo's Bizarre Adventure, in which a Stone Mask, created by the ancient Aztec people and notable for being used to turn recurring series villain Dio Brando into a vampire, was an important relic in Part 1, "Phantom Blood".

The Clock Tower area is the same as the clock tower from Rondo of Blood, the game's predecessor.

In the Spoiler:Reverse Colosseum part of the Upside-Down Castle, there is a boss fight with three ghosts that are named Fake Trevor, Fake Grant and Fake Sypha. These are the doppelgangers of the characters from Castlevania III: Dracula's Curse, with whom Alucard teamed up with to defeat Dracula.

In the Inverted Castle, the player must unite 5 relics of Dracula in order to unlock the path to Dracula (Those being a Ring, Heart, Rib, Tooth and Eye of Vlad), a concept first utilized in Castlevania 2. All five are guarded by bosses based on the original Castlevania bosses.

In addition, every boss in the Inverted Castle save one are previous bosses and even playable characters in the series. Aside from the aforementioned five, the player meets Galamoth (Kid Dracula), Shaft (Rondo of Blood), the Doppleganger (Castlevania 3), three falsified heroes from Castlevania 3, with whom Alucard himself was a companion, and of course Dracula. The one exception is Beelzebub, whose first appearance was Symphony of the Night.

The optional boss battle at the top of the Inverted Castle, Galamoth, is a villain from the Kid Dracula series. Although his design is far more gothic and gritty to coincide with Symphony of the Night's style, he retains basic design similarities and even similar lightning based attacks.

There are two familiars that didn't make the cut during the transition to the Western market. These are the Half-Fairy and the Nose Demon. They are almost exact copies of the normal Fairy and Demon, but with different graphics. They are still programmed into the Western version, but their familiar cards are no longer available, and thus have to be activated using GameShark codes.

A debug room can be accessed using GameShark codes, which features some testing tiles, and a Japanese voice track, which when translated reads:
"Hi, I'm Joji Yanami. I'm not a young man anymore. I've done this job for a long time. Eyup. I've done a lot of stupid roles. Man, though, this year has been so hot, I could die. It's way too much... I'm an old man, you see. I can't do anything anymore. It's exhausting. Someone save me, please. It's already September. I think something will come of all this, maybe. Old age is old age. Maybe not, though. Yeah. Well, that's all. See you, then."

There are a large number of unused dialogue pieces in the Symphony of the Night's data, including what may be an unused ending. Many of these sound files are alternate versions of voices that are already used in the game, but extended or slightly different.

A series of clips can be found in the game's sound files, which seem to be an unfinished ending. It seems to suggest that Maria intervenes in the fight between Alucard and Richter, where she becomes possessed or transformed by Shaft. It includes both winning and losing quotes, and ends with Alucard reflecting on the apparent death of both Richter and Maria. While the PlayStation Portable and Saturn versions allows a fight with Maria, it is not under these circumstances. There are no other suggestions towards this ending, but it is assumed to be an alternate ending during the fight with Richter when not using the glasses.

With the Lyric Card equipped, the player can activate a secret lullaby from the Fairy if Alucard sits in a chair for a period of time. This was only available in the Japanese version of the game, as the familiar that sings it was removed from the international release. But, Konami actually went out of their way to translate this song into English for the PSP version, too.
(Attachment will play both Japanese and English.)

The Saturn version includes a number of extra areas and features unavailable in the PlayStation version. Most infamously being that of the Underground Garden, as the entrance is still visible in the PlayStation version, though inaccessible. The player can glitch the game into allowing access to this area, but it is unfinished and only a glitched out save point is available.

When using the Rune Sword, the word "Verboten" will appear in its arc. This means "Forbidden" in German.

Dracula's castle in the boxart of the USA release is Mont Saint Michel, in France.

If Alucard remains seated for a long period of time, he will fall asleep with visible "Z"s. If you have the Fairy familiar, she will also take a rest on Alucards shoulder, only to stumble when he gets up again afterwards. She will also do this if Alucard remains stationary for a prolonged period of time.

Every so often, when Alucard is turned to stone, there is a chance that he will become a giant stone gargoyle. This will make him invincible, but of course unable to do anything.

When inserting the game disk into a CD player or PC and attempting to listen to it, a message from Alucard can be heard which says:


A similar message from Alucard's Japanese voice actor exists in the Saturn version.

After his message finishes, you'll then be treated to an untitled electronic remix of the "Dracula's Castle" theme.

At the start of the game, Death will take Alucard's equipment. Continuing to the Alchemy Laboratory, and then immediately returning to the room Alucard met Death, the player will be faced with Slogra and Gaibon (the first boss fight). As soon as the player attacks either of them, Gaibon will grab Slogra and fly off, only to be met again in their usual place.