Demonica and Malicia are the twin mistresses of evil in the Captain Proton holodeck serial, roles played by the Delaney sisters of stellar cartography at the start of Thirty Days.
Demonica and Malicia are characters in The Adventures of Captain Proton, Tom Paris's black-and-white holodeck pastiche of 1930s film serials. They appear in the fifth-season Voyager episode Thirty Days.
The pair are scheming twins who take Captain Proton's sidekick Buster Kincaid prisoner. They are played by Jenny and Megan Delaney, twin sisters from Voyager's stellar cartography department who had been mentioned since the first season but had not been seen until this episode.
The scene is mostly an excuse for comedy about Harry Kim's love life: as Kincaid he is tied up between the two, and afterwards confides to Paris that he is interested in one sister while it is the other who keeps pursuing him.