Cassie was in charge of a diner after her mother ran off. She lived near Roswell and Area 51 and knew the area well. One day in 1958, while she was serving coffee to her friend Jimmy Stalkingwolf, the Doctor walked in and activated a device from an alien crash landing. Secret agent Mister Dread quarrelled with Jimmy, forcing Cassie to flee with the Doctor and Jimmy. The Doctor, Cassie and Jimmy became prisoners of the military. After discovering the military were working with the Viperox to gain control of the Earth, Cassie and Jimmy helped the Doctor defeat them. Cassie was devastated when the Viperox attacked the local town.
She also helped Seruba Velak escape. After defeating the Viperox, the Doctor left Cassie and Jimmy with the job of rebuilding the town. (TV: Dreamland)
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.