Roboform

Roboforms are robots who are scavengers. They travel alongside invading alien forces who take anything on the planet of value to them before the main threat arrives. The Doctor likened them to pilot fish, as well as the main threat to a metaphorical shark.

Appearance
Roboforms are humanoid robots with featureless, gold-coloured heads that vaguely resemble skulls. They are often seen wearing full-length black cloaks that conceal most of their bodies, save for their faces. When on Earth, they were full-body outfits consisting of bulletproof Santa Claus suits and metal masks to help them blend in.

Technology
In their Santa Claus disguises, the Roboforms were often seen playing music with instruments such as trumpets, trombones, and tubas. However, they could also be used as weapons such as machine guns, flamethrowers, and rocket launchers. They also use a remote-controlled Roboform Christmas Tree, and bombs disguised as baubles. When undisguised, they use basic machine guns.

History
During Christmas 2006, the Roboforms were travelling alongside the Sycorax when they become attracted to the energy that the Tenth Doctor had released after his regeneration. They put into place a plan to kidnap him and use his energy to power their ships. On 24th of December that year, the Roboforms attacked Rose Tyler and Mickey Smith whilst they were Christmas Shopping. However, their targets managed to escape and their missile launcher operator was killed when a Christmas tree fell on him. The surviving Roboforms then sent a remotely-operated robotic Christmas Tree to Jackie Tyler's house in another attempt to kill the Doctor's friends. However, the Doctor woke up from his exhausted state and destroyed the Christmas Tree by blowing it up with his Sonic Screwdriver. Then, the Doctor drove the Roboforms off the face of Earth.

The next year, in 2007, the Roboforms were controlled by the Empress of the Racnoss, who used them to keep track of Donna Noble. A quartet of them tried to kidnap her following her disappearance from her wedding. Later on, six of them ambushed her at her wedding reception with exploding Christmas Baubles, but they were stopped by The Doctor, who used a sonic pulse created by firing his sonic screwdriver through the reception DJ's amplifiers, destroying the Roboforms. When the Doctor arrived at the Empress' underground lair, more Roboforms had arrived to defend her. Luckily, the Doctor, disguising himself as one of them, disabled them by using a remote control to make them 'relax'.

In 102 BC, the Roboforms became part of a massive group known as the Alliance, which formed to imprison the Doctor in the Pandorica beneath Stonehenge.