Roboform

Described as pilot fish by the Doctor, these Robot Santa Clauses would by used by invaders at Christmas to spread terror throughout the planet. The Robot Santas are humanoid and dressed up in Santa costumes, but had obviously fake masks. In their first encounter in 2006, they were attracted by the energy being released by the Doctor and wanted that source of energy themselves. (DW: The Christmas Invasion) In the second invasion of 2007, they worked for the Empress of the Racnoss and were helping her in her plans. (DW: The Runaway Bride)

Their actions imply that the Robot Santas are mercenaries who stick with the most powerful forces (either the Sycorax or the Empress of the Racnoss).

These robots were armed with either trombones that fired mortars, trumpets that fired bullets, tubas that were used as flamethrowers, remote controls that were used to control the Robotic Christmas Trees, and possibly more.