Donna's World is the alternate universe created when Donna Noble turned right, instead of left; while deciding to go for a job interview to become a personal assistant.
Origin
While on Shan Shen, Donna Noble was unknowingly fitted with a time beetle, also known as the Trickster's Brigade. A fortune teller selected a point in her life where making seemingly random choice had enormous ramifications:
In June 2007 Donna had to make a choice between two jobs. Her agency had offered her a contract with H.C. Clements, which while temporary, was posh and in the center of London, which Donna liked. Her mother, Sylvia Noble however, had managed to get her another job opportunity to become the personal secretary of Jival Chowdry, owner of a Photocopying business. Although this would be a permanent job, Donna found it less interesting.
While driving and in discussing the dilemma, Sylvia pressured her into "turning right" to stop by Jival Chowdry for a chat.
While in the regular timeline Donna ignored her mother and turned left, in this timeline she turned right, resulting in her taking the PA job.
Alternate Timeline
25 December 2007 - During the Racnoss crisis at Christmas 2007. Just as in the main timeline the Webstar was destroyed. However, the Doctor did not survive his encounter with the Empress of the Racnoss. UNIT recovered the body, declaring him dead, and speculating he died too fast to regenerate.
Donna witnessed the recovery, and met Rose Tyler for the first time. At this point Rose was not aware of Donna's importance.
Some time after this UNIT recovered the TARDIS from the Thames.
- In the main timeline, as shown in The Runaway Bride, Donna of course met the Doctor due to working at H.C. Clements which turned out to be a conspiracy of the Empress of the Racnoss. Donna's help saved the Doctor's life in that timeline.
April 2008 - By this time the Thames were stil closed off due to the Racnoss incident. This made business very hard for Jival Chowdry's company and she is sacked from her post as his personal assistant.
At the same time, the Judoon H2O Scooped the Royal Hope Hospital to the Moon. All patients and staff present the hospital died of oxygen starvation, with the exeption of Oliver Morgenstern, who was passed the last oxygen cylinder by Martha Jones. Martha herself died, as did Sarah Jane Smith, who was investigating strange occurences in the hospital. Sarah Jane's companions, Luke Smith, Maria Jackson and Clyde Langer were also assumed dead.
During the evening of this day, Donna again met Rose Tyler. During this encounter she started to suspect that Donna might have some importance, and warned her to leave London for the far-off Christmas holidays.
- the regular version of these events were shown in "Smith and Jones". The Doctor (alias, Mr Smith) investigated the hospital instead of Sarah Jane Smith, and saved all the people by finding the Plasmavore culprit in time. He took on Martha Jones as a companion.
- The events of The Lazarus Experiment and The Sound of Drums presumably never happened, as the Doctor, Martha and Captain Jack Harkness never went to Malcassairo in the year, 100,000,000,000,000; to remind Professor Yana that he was the Master, as they did in the main timeline during "Utopia". So the Mr Saxon regime could never have started. This would mean that in this reality, the Master is still alive but he is yet to know of his true identity.
25 December 2008 - Donna and her family are out of the city, as they have won a Christmas holiday. A Titanic replica crashes into Buckingham Palace, destroying the entire city of London, and flooding the lower half of England with radiation.
In the weeks thereafter, an emergency government was set up and seven million people were evacuated to cities such as Leeds and Glasgow. People in these places were evicted for small reasons such as missing a single mortgage repayment, to make up for the lack of housing. Refugees lived with several families cramped together in these houses, and had no voting rights. Syliva noted that it was as if they didn't exist.
The Nobles are moved into a house in Leeds.
- The regular timeline shows the disaster closely averted by the Doctor, in Voyage of the Damned. While the city was nearly abandoned in the regular timeline, this seems to not have been the case in the alternate timeline.
America promised 50 billion pounds in financially help for Britain, however this fell trough when the Adipose chose this country for their birthing program, and sixty million Americans across the country were fully transformed into fat.
- In the regular timeline the Adipose chose the United Kingdom for their scheme, but were stopped by the Doctor and Donna before their plan could be put into full swing, as shown in Partners in Crime. Supposedly the change of location was the result of the crisis in Southern England.
As Britain is in such an unstable situation and other countries have closed their borders-- so deportation is out of the question-- they start sending "immigrants" to Labour camps. The Nobles lived with one of the families getting sent away. Wilf, who served during World War II, is in horror. Seeing parallels between this and the Nazi regime which caused the Holocaust, saying that it had the same reasoning as "the last time".
2009 - The Sontarans invaded the Earth. Due to the crisis, the United Kingdom is hit less by the ATMOS gasses than other nations such as China. Torchwood-3 successfully tries to stop them. However, Gwen Williams and Ianto Jones sacrifice their lives in the process. Captain Jack Harkness is shipped of to Sontar, presumebly Torchwood, atleat the Cardiff branch, has now disbanded.
Rose Tylor meets with Donna Noble again, this time apparently aware of her importance, and working with UNIT. Rose remarks to Donna that they were the last ones left.
- The Sontaran Invasion of Earth was covered in the fixed timeline during The Sontaran Stratagem" and "The Poison Sky", where it was stopped by the Doctor with the help of UNIT, Martha Jones and Donna Noble. Torchwood seemed to clear the atmosphere from ATMOS much the same way the Doctor did.
Negation
UNIT and Rose Tyler send Donna back to the time where the world split. Donna must make herself turn left. She runs out of time, and realises that the only way to change the timeline is if she is ran over, blocking her past self from driving round that way.