From TARDIS Index File, the free Doctor Who reference.

Graske
Place of origin:	Griffoth
Appearances:	Graske - List of Appearances
Notable Individuals:	Krislok

The Graske were humanoid creatures from the planet Griffoth, known for a being a troublesome species.

Biology

The Graske were small compared to humans and had pebbly brown skin and three tentacle-like features on their heads. (DW: Attack of the Graske) They had difficulty speaking other languages, having odd grammar and curt sentences. (SJA: Whatever Happened to Sarah Jane?, DW: Music of the Spheres)

Since every Graske that has appeared looks and sounds the same it is possible they are a clone race like the Sontarans.

Krislok the Graske. (SJA: The Temptation of Sarah Jane Smith)

Technology

The Graske were a time-active species and could travel by different methods. Individuals could travel through time with ease, using a device on their belt to vanish in a distinctive blue glow. The Graske employed by the Trickster also had a gun which he could use to take people out of time and put them into Limbo. It could also reverse the process, putting them back in time and space and restoring their timeline. (SJA: Whatever Happened to Sarah Jane?)

When invading a planet, they replaced the inhabitants of the planet with changelings. This process was quick, with the Graske replacing the individual with the changeling in seconds. The originals were then stored on Griffoth in stasis chambers in order to maintain the copy. The changeling could be identified by its glowing green eyes. (DW: Attack of the Graske)

Graske also had conventional spaceships for travel. Krislok was capable of disguising himself as a Human child. (SJA: The Temptation of Sarah Jane Smith)

History

The Graske were conquerors, though unlike other species they did not take a planet by force. They would instead use their changelings to systematically replace the inhabitants of the planet. (DW: Attack of the Graske)

It is believed that at one point the Graske may have attempted an invasion of Earth, stealing people from various Christmases from across time, which was stopped by the Doctor and one of his companions by reversing the capturing process, returning the hosts. (DW: Attack of the Graske)

Due to its unique nature (it was in fact an interactive adventure), the canonicity of Attack of the Graske is unclear; the events may have still happened, but not necessarily as depicted on air.

A Graske named Krislok became a slave to the Trickster after the Trickster agreed to save its life during what would have been a fatal crash. (SJA: The Temptation of Sarah Jane Smith) He was used by the Trickster to remove Sarah Jane Smith and later Maria Jackson from time. The Graske succeeded both times, but Maria managed to escape into 1964. The Graske recaptured her again, but then got sent to capture Alan Jackson. Alan fought the Graske and beat it, forcing it to tell him where his daughter went. The Graske later escaped by wriggling its way out of its bonds. (SJA: Whatever Happened to Sarah Jane?)

In 2009 the Graske home planet of Griffoth was stolen by the Daleks and relocated to the Medusa Cascade, later the Daleks were defeated and Griffoth was sent back to its original position in space. (REF: The Time Traveller's Almanac)

Later, the Trickster had Krislok pose as a small boy to lure Sarah Jane into a trap set at the time of her parents' death. In the alternative timeline created, the Graske was charged with enslaving humanity to do the Trickster's bidding. Clyde Langer and Rani Chandra convinced Krislok to help them, and they gave him the puzzle box to protect him should the Trickster seek revenge. (SJA: The Temptation of Sarah Jane Smith)

A Graske in the TARDIS. (DW: Music of the Spheres)

There is an unconfirmed report that a Graske also managed to invade the Doctor's TARDIS and used a space portal to travel to Earth. The Doctor managed to close the portal and send the Graske back to where it came from. (DW: Music of the Spheres)

As with Attack of the Graske, the interactive nature of this mini-episode, in which the Doctor interacted with audience members watching the episode at the 2008 Doctor Who Prom concert, is of uncertain canonicity.

One Graske was captured by the Krulius and stored in a hologram. (WC: Monster Hunt)

In 2010 a Graske was seen at a bar where the Doctor came to visit Jack Harkness one last time before his regeneration. (DW: The End of Time)

Behind the Scenes

• As indicated above, the first two Doctor Who-related televised appearances of the Graske are of uncertain canonicity as both were interactive, fourth wall-breaking episodes. The first definitively canonical appearances of the Graske were in two episodes of The Sarah Jane Adventures. The first of these, Whatever Happened to Sarah Jane?, makes a possible oblique reference to Attack of the Graske when Sarah Jane Smith makes reference to there being "some Graske activity" on earth a couple of years prior. The first indisputably canonical appearance of a Graske in Doctor Who proper was as a patron of a bar in The End of Time.