Victoria Waterfield was a companion of the Second Doctor, leaving with him after her father was killed.

There have been at least four separate K-9 units in the series, with the first two being companions of the Fourth Doctor.

Rose was a companion of the Doctor.

He was a companion of the Fifth Doctor, being a regular in the programme from 1983 to 1984.

Both characters had been companions of the Fourth Doctor, but they had not appeared together before.

Sarah Jane tells Clyde that she has researched many previous companions of the Doctor and what they are doing now.

He was a companion of the Fourth Doctor.

River Song was first seen in the series as a future companion of the Doctor.

The companions or assistants of the Doctor of the Doctor Who television series.

Leela was a companion of the Fourth Doctor and a regular in the programme from 1977 to 1978.