History Theatre / TheStrangeCaseOfDrJekyllAndMrHyde

* YourCheatingHeart: Enfield cheats on Helen, his fiancee. It's technically before they're married, but he implies he'd continue doing it afterwards.

* DisabilityNegatingSuperpower: Jekyll has a deformed hand; Hyde doesn't. Depending on the production, Jekyll also wears glasses that Hyde doesn't need.

* ChekhovsGun: [[spoiler:In an early scene, Jekyll and Helen discuss the fact that the published version of Jekyll's formula contains a printing error that would make the resulting concoction lethal, killing its recipient in seconds. In the final scene, Hyde forces Helen to make up a fresh batch of the serum for him, and warns her not to deviate from the recipe. She makes the batch using the published formula, leading to Hyde's death.]]

* ChekhovsGun: [[spoiler:In an early scene, Jekyll and Helen discuss the fact that the published version of Jekyll's formula contains a printing error that would make the resulting concoction lethal, killing its recipient in seconds. In the final scene, Hyde forces Helen to make up a fresh batch of the serum for him, and warns her not to deviate from the recipe; she makes the batch using the published formula, leading to Hyde's death.]]

'''Hyde:''' Am I mad? Making love to those I love, and killing those I hate--is that madness, or is that just doing away with the formalities?

* AdaptedOut: Sir Danvers Carew, Hyde's murder victim in the novel, isn't mentioned or seen.

* NeverHeardThatOneBefore: When he first meets Helen, Jekyll quotes Faustus's speech on meeting Helen of Troy in ''Theatre/DoctorFaustus''; she finishes it with him, and notes wryly that she's heard it "fairly often".

* PragmaticAdaptation: In the original novel, Utterson's investigation is the main plot, but now Hyde's secret is too well known for that to work. The play keeps Utterson's investigation, but only in the second act, and plays it mainly for dramatic irony as Utterson struggles to catch up to what the audience already knows.

* {{Symbolism}}: Lots of symbols of duality -- the two narrators, the two women, a riddle about something with two faces that are identical but different, a philosophical aside about whether a zebra is black with white stripes or white with black stripes, a character with a twin.

** When he first meets Helen, Jekyll quotes Faustus's speech on meeting Helen of Troy in ''Theatre/DoctorFaustus''; bits of the speech come back several times later in the play with ironic twists put on them.

** When Hyde first meets Cybel, she tells him, "I've got a soft spot for the misfit type, and I'd say you are that." At the end of the play, a policeman says, "Don't I know you from somewhere?" and she replies, "I don't know -- are you the misfit type?"

* HowWeGotHere: The second act is structured like this; it opens with Utterson arriving at Jekyll's house for the final showdown, then recounts his investigation in a series of flashbacks, before continuing on to the showdown itself.

* YoureInsane: Seen in this exchange ate in Act II.

* YoureInsane:

'''Hyde:''' Am I mad? Making love to those I love, and killing those I hate -- is that madness, or is that just doing away with the formalities?

* AscendedExtra: Utterson's kinsman Richard Enfield is a major character; in the novel, he only appeared in a couple of scenes, and his only significant part in the plot was to witness the incident of the girl and the cheque.

* AnimalTesting: Jekyll first tested his formulas on animals, resulting in a lab strewn about with dead and deformed rabbits before he hits on the correct mixture.

** During his confrontation with Lanyon at the end of the first act, Jekyll attempts to draw a line between Hyde's actions and his own. "I didn't do it! Hyde did!" By the end of the play, however, he's accepted his responsibility, and uses "I" throughout his confession to Utterson in the final scene.

** Utterson's butler is also killed by Hyde after coming to Enfield's defense.
** Lanyon dies sooner and more dramatically in the play than in the original novel, with Hyde killing him personally.

* AnimalTesting: Jekyll first tested his formulas on animals, ending up with a lab strewn about with dead and deformed rabbits.