The pan-dimensional beings originated from a location known as Trilazzx Beta. They can exist in seven to eleven dimensions at once, and are known for their "horrible sense of direction."
30 million years prior to the events of the series, a group of pan-dimensional beings crash-landed their spacecraft, creating the valley that would one day host the modern-day town of Gravity Falls, Oregon, as well as forming the bizarre floating cliffs surrounding the land. As time passed, the surviving crew died off while their ship was buried beneath the surface.
Judging the remains visible in their spacecraft, each being has at least four limbs, and wore helmets when in space.
The moniker of "pan-dimensional beings" is possibly a reference to the interdimensional beings in the movie Indiana Jones and the Kingdom of the Crystal Skull.