The Graskes are Body SnatchersThe Graske come from the Planet of Griffoth and they are small Creatures. A Graske carried round a Space-Time Transmat and a Blaster. When the Doctor and Rose met the Graske he stole a lot of Aliens and made Duplicates of them like Humans, Slitheen and Scholars. The name for the Duplicates is Changelings which could be spotted because of their Green Eyes. Meanwhile the real Aliens were stored in a Chamber on Griffoth. The Names which were considered for the Graske were Griffak, Gr'thaaak and Graak. The Graske had to keep the real Aliens alive in their Pods because the Duplicates had to stay alive. The Entrance to the Griffoth Chamber was very heavily shielded. The Doctor did figure out a way of getting inside but he had to solve a Series of Puzzles. The Graske appeared in the 21st Century Earth but stole 2 Welsh Family before he could run away to 1883.
Years later the Graske returned inside the Tardis as the Graske lied to the Doctor saying that there was a Space Portal to Earth that was Dangerous. The Graske just wanted a shortcut to Earth but when the Doctor found out he banished the Graske to the other side of the Galaxy.
The Graske have appeared in 2005 Christmas Special: Attack of the Graske
2009 Muscial: Music of the Spheres