Out of all the Batman the animated series episodes, this is the only one to ever mention the Joker's (assumed) real name, Jack Napier. In addition, the name appears on the Joker file in Joker's Wild (1992).
While hallucinating, Batman makes a passing reference to Jason Todd, the second Robin. Batman raves "Robin... look out... Joker's got a bomb!", which in the comics is how Jason died.
Batman allows a doctor to take a blood sample without retrieving it after she studies it. This means she has his DNA and thus could discover his true identity.
"Dreams in Darkness" got its start when Batman story editor Michael Reaves asked Judith Reeves-Stevens &
Garfield Reeves-Stevens to adapt the Garfield Reeves-Stevens short story, "Masks," which appeared in the anthology, The Further Adventures of the Joker.
Whilst the Joker's first laugh in this episode sounds like Mark Hamill's portrayal, the second and third sound are far too high-pitched. Loren Lester, Robin's voice actor, stepped in to fill the role for the episode.