Trickster's Brigade

The Trickster's Brigade were a group of creatures apparently led by the Trickster (Captain Jack's Monster Files, Doctor Who Confidential).

Like their leader, the Brigade sought to change the normal course of history by altering details in individuals' lives. According to the Tenth Doctor, most of these changes were "tiny" and ones that the universe could "compensate" for. However, if the Brigade's victims had a particularly great influence on the universe, the change would create an entire parallel world around that person.

The Brigade caused the formation of parallel universes around two of the Doctor's companions, Sarah Jane Smith and Donna Noble (SJA: Whatever Happened to Sarah Jane?; DW: Turn Left). Both of these parallel universes were closed off when the two women were returned to their rightful place in time.

Time Beetles were the only beings definitively identified by the Doctor as "one of the Trickster's Brigade", but this language implied the existence of others.
 * It is logical to infer that Krislok the Graske employed by the Trickster (especially with its brief appearance in Captain Jack's Monster Files when discussing the Trickster's Brigade), as well as a Fortune Teller who seemed to be working with Time Beetles, may also be members of the Brigade. Andrea Yates may also be said to be a de facto member, since she consented to be used by the Trickster.