If you are referring to something from the TV Series, please say so for the benefit of those who haven't seen the series yet.
One of the (many) nagging differences between Stargate and the various follow-on series is the depiction of the Goa'uld. In the movie, Ra appears to be a human boy possessed by a Grey alien, while in the series, the Goa'uld are parasitic snake looking things. Perhaps Ra was simply a different kind of alien, and somehow ended up working his way into the Goa'uld's setup. Or maybe he started as a Goa'uld, and was possessed by a different alien in turn, with the two aliens' origin stories being mixed up by the humans on Abydos.
- Or, the Grey alien was an earlier form of Asgard, and his last host.
- The RPG says Ra's previous host was indeed an Asgard.
- IRL: This is just one of many examples of how SG-1's canon disregarded the film. Ra appears briefly in Continuum, played by a different actor and is a Goa'uld system lord just like any other.
This is a reaction to the very good Headscratchers question "How did they dial the gate from the Abydos side?". Unbeknownst to them they lucked out with this. There was just enough charge in it to dial once.
Stargate SG-1 allows for alternate realities - several shows have touched on this. This neatly explains the differences between the movie and the resulting series.
Let's forget the eventual TV series, and look only at the original film. People other than me have speculated that they were given the first six symbols and they could have brute-forced the seventh in an afternoon. For some reason, they didn't do this. There are six symbols in the cartouche in the center of the cover stone, why would they even try a seventh? There are nine chevrons on the Stargate, why seven? Forget the TV show.So they bring Daniel Jackson in. Daniel is shown the cover stone, which consists of a copy of the Gate's ring, an Egyptian inscription vaguely detailing the burial of the gate, and a cartouche containing 6 of the symbols from the Gate's ring. He's not allowed to know of the existence of the gate itself—Colonel O'Neil stops Dr. Shore from telling him mid-sentence. Given this alone, Daniel does the following:A: "Corrects" the translation of the inner track of normal Egyptian Hieroglyphs. This correction is meaningless; "forever" becomes "for all time," "Doorway to Heaven" becomes "Star Gate." No conclusions are drawn from the "more accurate" translation of the inscription, and it's done just to make Daniel look smart.B: Takes two weeks to realize the symbols drawn on the gate are not words but star constellations. By picking out Orion, which most folks would recognize instantly.C: Somehow, given the above information, he makes the astonishing leap to the conclusion that the constellations somehow stand for fixed points in space, six of which are required to draw three lines of position to get a fix, and then a seventh symbol as a point of origin, and that the cover stone is detailing the operating instructions for a celestial navigation system even though he doesn't know about the Stargate yet.D: When asked "Seven symbols, there are only six in the cartouche?" He responds that the seventh is built into the bottom of the cartouche rather than inside it proper. And despite the circle over chevron "Earth point of origin" symbol we all know and love being on the cover stone, he doesn't make this connection until he sees it going past on the monitor once he's shown the actual gate. It's not "Here it is, it's this pyramid shape, it's here on the outer track, 14 clockwise from the top."I submit that Daniel completely misunderstood how the gate works, and only contributed by noticing "Hey, there's a seventh symbol here."