Bi-generation
Bi-generation was a variant of regeneration which the Doctor believed to be a myth. Instead of one incarnation directly transforming into the next, bi-generation caused the new incarnation to split from the previous, allowing the two to become independent beings.
The Fourteenth Doctor experienced a bi-generation after being gravely wounded by a Galvanic Beam. This resulted in him continuing to exist as an incarnation distinct from the newly created Fifteenth Doctor, although this new Doctor's consciousness continued from the Fourteenth's after his rehab. The process was assisted by Donna Noble and Melanie Bush who each grabbed and pulled the Doctor's arms to separate the two incarnations who both remembered their whole lifetime prior to the bi-generation.
The Fifteenth Doctor later caused the TARDIS to undergo a bi-generation of its own using the fact that he had won a prize for defeating the Toymaker so that both Doctors had their own TARDISes. He was able to accomplish this as the Toymaker and his rules still lingered for a few moments after his defeat. (TV: The Giggle [+]Loading...["The Giggle (TV story)"])
Effects
Bi-generation internalizes and builds up regeneration energy that would normally be expelled. This will cause discomfort, forcing the one undergoing the process to need help being pulled pulled in opposite directions to initiate the release; once the heads have separated, the previous incarnation and the new one momentarily share the body like conjoined twins, with each of them have the leg and able to pull the arm from the other's side out. They need additional help to fully separate.
Whatever clothes worn by the one regenerating is split between the two. In the case of the Fifteenth Doctor, he got the dress shirt, tie, underpants, socks and shoes of the Fourteenth Doctor; giving the newer incarnation some modesty. (TV: The Giggle)
Behind the scenes
- It’s unknown if bi-generation allows both the original incarnation and the one produced by this process their own regenerations, or the new incarnation is the only one who can regenerate.
- In the in-vision commentary for The Giggle, Russell T Davies suggested that the bi-generation affected the Doctor's whole timeline so that previous incarnations may have continued to exist beyond their on-screen regenerations.
- This mirrors the audio drama series The Nest Cottage Chronicles by Paul Magrs, which was intended to depict a retired Fourth Doctor after his regeneration.
