Analysis of information sources in references of the Wikipedia article "Companion (Doctor Who)" in English language version.
The Doctor allows Craig to come along and play the part of his companion [...]
A minor factor in the continual swirl around Doctor Who is that what constitutes a Doctor Who companion is no longer clear. Sure, Rose, Martha, and Donna were all companions. So was Captain Jack. But what about Mickey and Jackie? How do you qualify? Name in the opening credits, regular trips in the Tardis? The Doctor kisses you? I'm no longer sure. Modern TV drama is so difficult.