Saibra was originally named Sabra and she originally gained her abilities by virtue of being half-Zygon. She was briefly the result of a laboratory experiment before becoming a mutant.
When Psi tries to lure the Teller away from Clara by visualising some of the galaxy's most notorious criminals, the mugshots he is seen accessing include a Sensorite ("The Sensorites"), a Terileptil ("The Visitation"), a Slitheen, an Ice Warrior, the Gunslinger (A Town Called Mercy (2012)), Captain John Hart from Torchwood (2006), Androvax and the Trickster from The Sarah Jane Adventures (2007), and Abslom Daak from Doctor Who Magazine.
The Teller was originally confined to a wheelchair, and was more insectoid in appearance.
Speaking about the premise for the episode, director Douglas Mackinnon said "What we wanted to do was a heist movie for Doctor Who (1963). I've watched virtually every heist movie there's ever been, and it incorporates things into it, but because it's Doctor Who, time travel is involved".
Steven Moffat came up with the concept for this episode years earlier before handing it over to Steven Thompson when he found a way to utilise it.