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Mr White was a highly advanced handheld game console that utilised holograms for entertainment purposes, giving the player the full 5D experience. He was in the possession of Ruby White. Mr White's name was suggested by Clyde, following Ruby's last name, his main colour and his similarity to Mr Smith.
He was a pocket sized, white, oval device with a blue screen. Mr White presented himself as friendly and affable, quickly making friends with Sarah Jane Smith's computer, Mr Smith. Ruby White brought Mr White with her when she assisted Sarah Jane and her group against the Dark Horde. She claimed to have dredged the computer out of a swamp. It was Clyde Langer who suggested calling the computer "Mr White".
It was later revealed that Mr White was of Qetesh origin, just like Ruby; he was the entertainment system on her prison ship and had been upgraded and reprogrammed to serve her. K9 reset Mr White to his original parameters, and Luke Smith used his 5D holograms to help defeat Ruby. Although Clyde wanted to keep Mr White, who was now just a games console, Mr White was placed in a safe inside Sarah Jane's attic.