(SPACE.com) An American video game company has revealed there is an unauthorized stowaway on board the Japanese spacecraft now in Earth orbit on its way to the International Space Station (ISS).

"Wheatley," the orb-shaped robotic companion from Valve Software's 2011 popular game "Portal 2," is flying aboard the Japan Aerospace Exploration Agency's (JAXA) latest H-2 Transfer Vehicle, the HTV-3, which launched on Friday (July 20) to resupply the space station. The character, in miniature two-dimensional form, is soaring through real space thanks to an unnamed NASA worker.

Valve announced on its website's blog that "thanks to an anonymous tech at NASA, Wheatley is actually going to actual space."

The one-eyed sphere, or "personality core" as referred to in the video game, is given its voice by English actor and comedian Stephen Merchant. On board the HTV, which is nicknamed Kounotori or "white stork", the robot's voice is offered in the form of a phrase engraved under Wheatley's likeness -- "In spaaaaaaace!"

(Portal 2 players may associate that quote with another of the game's personality cores, the so-called "Space Core," though Valve attributes it to Wheatley on their blog.)

Not officially endorsed

A photo posted on Valve's website shows what appears to be a circuit board with Wheatley's likeness laser-inscribed in one corner. The photograph offers no reference of scale for the component, nor from what instrument it may have originated. [9 Weird Things Launched on NASA Shuttles]

NASA has several scientific experiments and payloads on the HTV-3, which astronauts will unpack after capturing the spacecraft using the space station's robotic arm and then attaching it to the outpost on Friday (July 27). Among the U.S. payloads are an Earth-observation camera, two small satellites, and a communications and navigation test bed.

The lack of details may be because the Wheatley etching is unofficial.

"And please note that when we mentioned an 'anonymous tech at NASA' we weren't kidding," Valve explained on its blog. "NASA in no way officially endorses secretly laser-engraving characters from Portal onto their spacecraft."

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"Portal 2" video game robot launched into actual space