Dr. Jekyll and Mr. Hyde (known in Japan as Jekyll Hakase no Houma ga Toki, which loosely translated to "Dr. Jekyll's Hour of the Wandering Monstrosity", known in-game in that version as Houma ga Toki) is a horror-themed side-scrolling action game developed by Advance Communication Company and published for the Nintendo Entertainment System in both Japan (by Toho Cinefile-Soft Library on April 8, 1988) and North America (by Bandai on April 1989).
Loosely based on the 19th century Robert Louis Stevenson novella Strange Case of Dr Jekyll and Mr Hyde, Dr. Jekyll and Mr. Hyde has players controlling Dr. Jekyll, a doctor who has managed to hide the evil aspects of his personality with a potion. Armed with only a walking stick, he sets off across town in an attempt to reach his wedding with the charming Miss Millicent, only to become impeded by a variety of annoyances (such as animals and other townspeople).
As he becomes more angry (which is shown as its own separate meter), he eventually succumbs to his anger and transforms into the monstrous "Mr. Hyde". As Hyde, the game switches to a nightmarish alternate-reality where Hyde progresses in reverse and players must abate his anger by firing out "psycho waves" at demonic enemies (turning it into a more action-oriented game).
While the game received a small cult following due to the dual-personality gimmick, it received negative reception over time due to its complex structure (with concepts only explained in the manual), its repetitive music and level structure, and the difficulty and pacing regarding the Dr. Jekyll segment. It is often considered for inclusion on Worst Games lists.
The game consists of six levels, but the ordering of the levels differs between the original Japanese and North American version of the game. The Japanese version includes the levels City, Park, Alley, Town, Cemetery and Street. However, the North American version removes the City level and instead duplicates the Cemetery level, leading to an order of Town, Cemetery, Alley, Park, Cemetery and Street.
As Dr. Jekyll
The character of Dr. Jekyll walks to the right, and can jump to avoid obstacles, and can also jab with his walking stick. However, the stick is useless against almost all enemies, and is only capable of damaging angry bees. Therefore, most of the Jekyll gameplay comprises of jumping to avoid coming into contact with enemies, since defeating them is impossible.
As Mr. Hyde
As Mr. Hyde, the game auto-scrolls to the left and the level is mirrored backwards with a darker color palette. Hyde can jump much higher than Jekyll, but more importantly can also punch and throw a special ball which the box art describes as a Psycho-Wave which can kill enemies at a distance. The goal while playing as Hyde is to kill demons as quickly as possible to relieve the anger meter so that he may transform back into Jekyll. If the meter is not lowered quickly enough, or Hyde's life is depleted, he is struck by lightning and the game ends.
If the player advances further through the stage as Hyde than previously as Jekyll, it counts as Jekyll's evil side triumphing, and similarly Hyde is struck by lightning and killed. During the Hyde sections, it is also possible to pick up coins occasionally dropped by defeated enemies. These coins then may be used by Jekyll to ward off certain citizens and avoid possible encounters.
What story the game has is detailed in its manual; the game itself features no expository text to explain the scenario, though it is very loosely based on the Robert Louis Stevenson novel. Dr. Jekyll has created a potion that has separated the good and evil aspects of his personality. When he is happy, he will remain as himself, but when he becomes angry, he is transformed into the homicidal and violent Mr. Hyde. The basic plot follows Dr. Jekyll's attempts to reach his wedding with the charming Miss Millicent, on the other side of town. Initially, he sets out from his house with his walking stick towards the church. Along the way, a variety of citizens, animals and other obstacles attempt to impede his progress, causing him to either become hurt and/or more angry. When his anger reaches a critical threshold, Jekyll transforms into Mr. Hyde, and the world becomes nightmarish alternative-reality. Furthermore, Hyde walks in the opposite direction to Jekyll, away from the church. If Hyde manages to kill the monsters and demons, his anger level returns to normal and Hyde morphs back into Jekyll. If Hyde does not dispose of the monsters or is attacked himself, he is suddenly struck by a bolt of lightning and the game ends.
The game includes two possible endings. The standard ending will happen if and when Dr. Jekyll reaches the church at the climax of the sixth level. Jekyll then marries Miss Millicent and presumably lives happily ever after. The alternative ending can occur only if Mr. Hyde reaches the church (which is usually not possible given that Hyde is struck by lightning if he progresses further than Jekyll; the exception is the second half of the final level). A boss monster named Letule will appear in the form of a floating head, and if successfully defeated, Hyde will transform back into Jekyll and can marry Millicent in an elongated wedding ceremony. The ending shows a bolt of lightning with a silhouette of Hyde and a cross behind him, seeming to indicate that Dr. Jekyll's evil persona has been vanquished once and for all.