This was the first time the Doctor introduced himself as John Smith, although Jamie had randomly given that as the Doctor's name in The Wheel in Space.
David Troughton's appearance as Private Moor makes this one of (as far as I can tell) only three stories to feature a real-life parent and child in named roles, the others being The Abominable Snowmen and The Web of Fear, which both had Jack and Deborah Watling in them. There were other cases of unnamed roles - David Troughton had played an uncredited guard in The Enemy of the World with his father, and the haemovores emerging from the sea in The Curse of Fenric (allegedly) included Sylvester McCoy's children.
It's not a named role, but Tennants father also starred as an extra in an episode. The Unicorn and the Wasp, I think.