Origin of the Title:
- Undo is a computer command that erases the last change to a document reverting it back to an older state or negates the last change to the file being edited.
- The extension: The .gz file refers to Gnu Zipped file archives used on Unix systems to compress large files.
Near the end, Dom (Grace Gummer) reviews an encrypted e-mail sent by Elliot (Rami Malek). The sender of the e-mail was "The Plague" and the recipient was Eugene Belford. "The Plague" is the hacker alias of Eugene Belford from Hackers (1995)
Deleted Scene: Darlene (Carly Chaikin) is sitting on the porch of the safe house at night. She lights a cigarette and looks at a diamond ring. As Dom (Grace Gummer) comes out the front door, Darlene puts the ringbox in her pocket. Dom chastises her for sitting outside, though Darlene assures her she wasn't followed. Darlene is not allowed to finish her cigarette and tosses it.
Music:
- "New Sensation". Performed by INXS. Plays as Elliot (Rami Malek) implements his new plan to undo the hack.
- "Listen to Your Heart". Performed by Roxette. Plays as Joanna (Stephanie Corneliussen) and Sutherland (Jeremy Holm) are ambushed by Derek (Chris Conroy).
- "Renegades". Performed by X Ambassadors. Plays in the background as Elliot meets with Darlene (Carly Chaikin).
- "One Week". Performed by Barenaked Ladies. Plays on the FBI agent's telephone at the stake-out site.