The Montoon system was a star system with at least two planets. K9 Mark I visited the second planet from the star and observed the Ocean of Brains. His next incarnation later recalled this event to Starkey and Jorjie Turner. (TV: Curse of Anubis)
The Eleventh Doctor blamed picking Amy Pond and Rory Williams up late on the TARDIS's annual maintenance and a vortex repair in the Montoon system. (COMIC: Bus Replacement TARDIS)