A is for... Adipose

Creatures composed entirely of fatty tissue. When the Adipose breeding world, Adipose III, vanished, the Adiposian Royal Family entered into a scheme with Matron Cofelia to rear a new generation on 21st Century Earth. Posing as Miss Foster of Adipose Industries, she began selling a miracle diet pill - slogan: "The Fat Just Walks Away". Each subscriber got a small gold pendant as a free gift. This contained an electronic device which triggered fat in the users' bodies to transform into an Adipose youngster, who would be collected by her men later. This would take place at night when the person was sleeping. When two of the pendants were in close proximity, it could trigger a complete parthenogenesis - when the human's entire body would be transformed. When the Doctor, Donna Noble and a journalist named Penny Carter all began investigating the company, Miss Foster was forced to advance her plans. Adipose births were triggered all over England and a spaceship was called in from the home planet to collect the young. The Doctor tried to warn Miss Foster that what the Adiposians had done was against galactic law, as upheld by the Shadow Proclamation, and she would be regarded as a witness that the Royal Family would have to silence. They dropped her from a great height - literally and figuratively.
Later, during the period  when the Tenth Doctor was about to regenerate, he went looking for Captain Jack Harkness in an alien bar. The clientele included a drunken Adipose child.
Adipose III was one of the planets stolen by Davros and the Daleks to generate their Reality Bomb, and was returned to its rightful place by the Doctor-Donna.
To date, only infant Adipose have been seen - small white blobby creatures with a single fang in their mouths. We have yet to see what an adult looks like.

Appearances: Partners In Crime (2008) and The End of Time Part 2 (2010).

• The massed ranks of Adipose were computer generated using the same software employed to animate the vast armies seen in the Lord of the Rings movies, whereby each creature could move independently and not have to be individually programmed.