In a parallel universe, a girl called Ally was a fan of the show, Doctor Who. When the Eleventh Doctor came into this universe, Ally found him, and became his companion. She revealed to, much to his shock, that his adventures were all part of a television series. Among some things she asked him about were the silly-looking aliens from the early days, and if Elisabeth Sladen's death had affected Sarah Jane Smith. The Doctor revealed that the monsters in the show DID look like that, and that Sarah Jane was still alive and well.
Multi-adventures reference the rare instance when a companion is shown or stated to have multiple adventures with the Doctor but only appears in a single story.
If a medium is not mentioned, then this incarnation did not have companions who were original to that medium; it does not mean that this Doctor failed to appear in that medium.