Crash Site Omega is an alien spacecraft buried beneath Gravity Falls, Oregon, apparently having crashed millions of years prior to the present day and claiming responsibility for the odd appearance of the Gravity Falls cliffs. Ford Pines is uncertain whether the saucer is responsible for the Anomalous Phenomena in Gravity Falls, or rather that the presence of the phenomena is what drew the craft there to begin with.
Once a spacecraft belonging to an alien race known as the Pan-Dimensional Beings of Trilazzx Beta, creatures known for existing in 7 to 11 dimensions at once and having horrific senses of direction, the vessel crashed into Earth approximately 30 million years B.C.E., evidenced by tree ring interruptions and radiation tests conducted by Ford. The impact was responsible for the creation of 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 eons passed, the surviving crew died off while their ship was buried beneath the planet, ultimately creating numerous disturbances in the hamlet resting above it, such as electrical disturbances, sick livestock, and magnetic interference with vehicles.
Ford discovered the existence of the saucer some time after arriving in Gravity Falls, and he and his partner Fiddleford McGucket scavenged materials from it for use in their universe portal and other projects. Due to the ship having crashed millions of years ago, the passengers and crew were long dead, as well as most of the systems. In addition to collecting parts, the two geniuses spent time studying the aliens' technology and language.
In "Dipper and Mabel vs. the Future," Ford reenters the saucer with Dipper after recounting its history in order to locate a powerful adhesive needed to repair the container holding the interdimensional rift. While they succeeded in locating it, they inadvertently activated one of the ship's long-dormant security systems. Ford was taken captive by a security droid and sent flying towards space, bound for an intergalactic prison, but was fortunately saved by the quick actions of Dipper.