One thing about the man who calls himself the Doctor; he makes an immediate and memorable impression, even if that that impression is often more along the lines of ‘Who is this madman?’
Ask any of his companions and they’ll tell you, because each and every one of them has been irresistibly drawn to him in one way or the other, and none of those still living will ever forget him. They wouldn’t want to even if they could.
He sweeps into their lives out of nowhere, shows them everything they’ve been missing, then leaves.
They’re never the same again.