From the Huggsy Scriptures...
"Ridley Scott Defines Canon".
Ridley just stands in some guys yard. There's a large object next to him covered in a blanket.
"Ridley Scott? It's an honor sir. But what are you doing here?"
"I'm here to explain the concept of canon in the Alien universe."
"You see, canon is...(tears blanket away, revealing a large cannon)...what I say b*tch!"
He pulls a long string and the canon fires, destroying the dude's house. As the place burns, the camera is just behind Scott. While the guy is running around in his yard screaming hysterically and trying to fight the flames with his garden hose, Scott slowly turns his head back towards the camera, with a mischievous smile on his face. We then see the famous "end transmission" animation from the films, before everything fades out.