Bootstrap paradox

A bootstrap paradox was a sequence of events in which an event was among the causes of another event, which in turn is among the causes of the first-mentioned event. A common example was an individual who grew with a piece of music, then travelled back in time and introduced the song into the past, with the resultant question being: Who composed the song? (TV: Before the Flood)

The Twelfth Doctor once explained the paradox (TV: Before the Flood) to Clara in a mental TARDIS console room. (TV: Heaven Sent) A bootstrap paradox was created while the Doctor and Clara were at the Drum: the Doctor gained the idea of using a hologram of a ghost version of himself, through Clara who had seen the ghost Doctor and told the Doctor about it. (TV: Before the Flood)

The Bad Wolf entity's existence was the result of a bootstrap paradox. Rose Tyler only looked into the heart of the TARDIS, creating the Bad Wolf, after she was motivated by seeing Bad Wolf graffiti, which she created after becoming the Bad Wolf herself. (TV: Rose, Aliens of London, The Parting of the Ways)

Joel Finch inadvertently inspired the pose of God in Michelangelo's Creation of Adam for the Sistine Chapel, after having been sent back to 1511 by a Weeping Angel. Joel studied the works of Michelangelo in the 21st century, and suggested this new pose based on his own recollections of the painting. Joel may have also invented the sandwich. (AUDIO: Fallen Angels)

According to one account, the Fifth Doctor's recognition of the phrase wibbly wobbly, timey wimey, (TV: Time Crash) seemingly coined by his tenth incarnation, (TV: Blink) was as a result of hearing River Song say it during an adventure she had with that incarnation. (AUDIO: A Requiem for the Doctor) River herself learned the phrase from "her Doctor", the Eleventh, (TV: The Wedding of River Song, The Angels Take Manhattan) and assured the Fifth Doctor that it would grow on him in time. (AUDIO: A Requiem for the Doctor)