Dr. Jekyll and Mr. Hyde (NES)

Dr. Jekyll and Mr. Hydeis a game based on Robert Louis Stevenson's 1886 novellaThe Strange Case of Dr. Jekyll and Mr. Hyde''. It's as good as it sounds, assuming youreally'' hated the book.

Debug Features#

When the title screen menu cursor points to the "START" option, press B on Controller 2, then press Up, B, Right, Left, Down, Right, Left, A, B, Right, Select, B, Down, Start on Controller 1. During gameplay, on Controller 2, press A to skip the current level (up to the ending sequence) or B to switch between the Jekyll and Hyde modes.

Regional Differences#

Title Screen#

Japan	US

Copyright text was added.

Unused Graphics#

The Japanese version used a UNROM board with 128 KB of PRG ROM and 8 KB of CHR RAM. This board configuration allows graphics data to be loaded into the CHR RAM from the PRG ROM on the fly, instead of relying on a fixed graphics ROM. The PRG ROM itself contained 48 KB of graphic data.

When the game was brought to the US, the cartridge board was changed to use the MMC1 mapper with a 32 KB CHR ROM chip instead of CHR RAM. During the conversion process, the developers moved 32 kilobytes of game graphics from PRG to the CHR ROM. However, since the game originally had 48 kilobytes of graphics data, that meant 16 kilobytes were left behind in the PRG ROM. The PRG ROM size itself was not reduced, and the developers simply blanked out the first 32 kilobytes of graphic data moved to the CHR ROM. But they left the rest inside the US ROM, so we have at least 16 kilobytes of graphics data from the Japanese version left inside the US version, unused and inaccessible.

This is the reason they completely removed two original levels from the US version. Those dropped out 16 kilobytes of CHR graphics contained the background and sprite data for exactly two missing levels. And, since the PRG ROM size was not reduced, instead leaving the former graphic data part-blanked and part-unusable, that led to the strange situation where the US game has a larger overall ROM size despite losing a significant amount of accessible content.

Levels#

Because of stripping 16 kilobytes of 48 kilobytes CHR data during the cartridge type switching process (see above), they had to remove two original levels:

• Level 1 (city)

• Level 3 (alley)

To compensate, the cemetery and town levels are repeated twice. However, the stages' enemies were not changed to fit, which leads to most of them spawning out-of-bounds. Making things even more complicated, the order of the levels was rearranged:

Only the last two levels were left untouched between versions.

Enemies#

The following enemies and NPCs are exclusive to the Japanese version.

Despite not being included in the game, the North American version's instruction manual still lists all of the enemies and describes them.

Because some of these enemies have their own theme, this also results in the NES version not using the songs, despite still being in the ROM.

Mysterious Silhouette#

Japan	US

As the last boss explodes, a humanoid silhouette can be seen hanging from the cross on top of the church. The US version replaces it with a gas lantern.

Ending#

In the Japanese version, the bride waits for you outside the church's gate in the good ending. In the US version, she is not there.

Bomb Detonation Time#

In the Japanese version, the bombs vary in fuse time by level. In the US version, the time it takes for the bombs to detonate gets progressively shorter on each level.

Music#

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There are a few songs in the Japanese version that are used, but were cut from the US version, as some of the enemies were cut from the North American version.

In addition, there is an unused song. It sounds like it may have been used for one of the enemy themes, but no enemy uses it.