Puxatornee

Puxatornee was a planet placed under the protection of the Galactic Heritage. (PROSE: The Tomorrow Windows) The Doctor had visited the planet in 3012 and then again in his seventh incarnation with Mel Bush in 3090, while in search of leptonite crystals to defeat the Quarks. The Doctor and Mel, however, visited in two separate intersecting alternative timelines. (AUDIO: Flip-Flop)

Behind the scenes
The name of the planet references the (real) town of Punxsutawney, Pennsylvania, the setting of the oft-referenced comedy Groundhog Day, which stars Bill Murray as a character stuck in a time loop. Flip-Flop involves two intersecting time loops.