The Furlings were the fourth race in the great alliance with the Ancients, the Asgard, and the Nox. To the SGC's knowledge, they have never encountered the Furlings and don't know what they look like or even if they still exist. The Furlings are first mentioned in the episode, 2.16 "The Fifth Race".
The Furlings were one of the Four Races that made up the Great Alliance. Their writings are found, along with the Nox's, the Ancients', and the Asgards' in Heliopolis (1.11 "The Torment of Tantalus"). The Asgard mentioned them by name when they described the alliance to O'Neill (2.16 "The Fifth Race"). No description of a Furling was ever made, though Jack O'Neill believed from the name the species was likely "cute and fuzzy" (6.15 "Paradise Lost").
Although not much is known about the race as a whole, a group of the Furlings broke off and formed this small, isolated Utopian community. As Harry Maybourne described it: "They sent out representatives to meet and evaluate people from all over the galaxy and offer them a chance to join them. The scroll and the stone were the invitation." Jonas Quinn translated the doorway for where this stone key would be used: "only the righteous may pass". Harry Maybourne translated the scroll and stone, found by his rogue NID team, and decided to escape from the authorities by travelling to this utopia. He tricked Jack O'Neill and the SGC to letting him accompany them to the planet, and used the stone to jump through the one-way door to paradise. O'Neill was able to follow him.
The Furlings had advanced technology. The Furling technology transported the pair to the moon above the planet. Furthermore, they filtered any advanced weaponry from coming through: the zat Maybourne used in his escape was gone. More primitive Earth weapons, such as O'Neill's Beretta and P-90, were unaffected.
Jack and Harry found only ruins of a village and skeletal remains of the people that once lived there. They did not know where they were or how to get back. As Harry Maybourne became more despondent and erratic while eating an awful "arugula tasting" plant, Jack O'Neill did more investigations, discovering the remains of a Goa'uld on the planet, and forensic evidence that the people killed each other. He was able to figure out the "arugula" was poisoned, likely by the Goa'uld, but not before he too was being swayed by its effects.
In the meantime, Maj. Carter and the SGC teams could not figure out how to find them or activate the doorway again without the Furling stone. But eventually, Carter realized the doorway led to the planet's moon and a Tok'ra ship rescued Maybourne and O'Neill from the Furling world.
When Martin Lloyd wanted SG-1's opinion on his Wormhole X-Treme movie, the team read about their counterparts finally meeting the Furlings, imagining them to be teddy-bear like creatures (10.06 "200").
- To our knowledge, SG-1 has never met the Furlings.
In the episode, 1.11 "The Torment of Tantalus", we learn that there was an alliance among four highly-developed races. The Furlings were revealed to be one of the four in the episode, 2.16 "The Fifth Race". The other three were:
- Goa'uld - The Goa'uld snuck into an idyllic region for the Furlings to meet other races and literally planted poison (6.15 "Paradise Lost").
--Aurora 12:13, 18 July 2007 (PDT)