In the end of Portal 2, I fired the portal gun to the Moon. And it worked, which created a quantum tunnel between Moon's surface and Floor below Wheatley - sucking Wheatley out into space.
Throughout the entire Portal game series, we've seen that the highly experimental Portal Gun works only on white plain surfaces. To make a Portal on other plain surface, we even need to paint that with white gel. The surface of Moon is neither plain nor white. How did the Portal Gun work on it, then?