OK, so this is cool. The puppet head that appears on the UNIT monitors is actually Stooky Bill, who appeared in the first ever television image transmitted in the UK.*
Which was round about when some of the scenes shot for the Specials were set. Plus Russell said that the man seen entering the Toymaker's shop in the Christmas Day trailer was someone famous. People assumed he meant that actor but what if it's actually John Logie Baird buying the dummy from his shop...
* https://en.wikipedia.org/wiki/Stooky_Bill
Which was round about when some of the scenes shot for the Specials were set. Plus Russell said that the man seen entering the Toymaker's shop in the Christmas Day trailer was someone famous. People assumed he meant that actor but what if it's actually John Logie Baird buying the dummy from his shop...
* https://en.wikipedia.org/wiki/Stooky_Bill