A TARDIS was stolen by the Twelfth Doctor and Clara Oswald on Gallifrey. After the Doctor's memories of Clara were wiped, she and Ashildr used the TARDIS to travel around the universe.
History
After the Doctor plucked Clara away from her death by the Quantum Shade through the extraction chamber, they retreated into the Matrix, where they were followed by the General, Ohila and Gastron. The Doctor escaped, and materialized the stolen TARDIS around Clara.
They then took the TARDIS to the end of the universe, where the Doctor found Ashildr waiting in a chair, a chessboard set up for when the Doctor arrived. They discussed the Hybrid, and Clara used the sonic sunglasses to listen in on the conversation. The Doctor later entered the TARDIS with Ashildr, and decided that Clara needed a memory wipe of him so that she could live a normal life again. Clara convinced him to make it completely random, and the Doctor ended up wiping his own memory of Clara. After he was unconsious, Clara piloted the TARDIS to Nevada, Earth, and dropped him off, before despositing the TARDIS nearby and disguising it as a North American diner. Later, the Doctor went in, and Clara, knowing that he didn't remember her, gave him a lemonade and had him tell the story of his adventures on Gallifrey.
When the story was done, Clara opened part of the wall and stepped back into the console room, where Ashildr was waiting. She told Clara she couldn't fix the chameleon circuit, so the TARDIS was stuck looking like a diner. Clara said that was "awesome," and dematerialized the TARDIS out of Nevada.
Later, the TARDIS passed the Doctor's in space. (TV: Hell Bent)
Appearance
The TARDIS bore a strong resemblance to the original TARDIS stolen by the First Doctor and Susan, as seen in The Name of the Doctor.