Surgeon Simulator 2013's best-kept secret has been unearthed by enterprising fans, revealing a bonus in-game mission in which players perform zero-gravity surgery on an alien being.
The not-entirely-realistic sim title includes a variety of outlandish challenges, ranging from brain surgery in the back of a moving ambulance to a heart transplant for Team Fortress 2's Heavy character. The alien surgery mission, however, was hidden behind several layers of secrecy, requiring players to solve an ARG before revealing an access code. Fans ended up brute-forcing the solution, circumventing the ARG's final challenges.
The video above shows how to access the mission, and gives details on how to perform its required "gobbleshaft transplant." What's a gobbleshaft? You're the surgeon -- you figure it out.