Sigourney's bump and a great YouTube moment that never was.

Have you seen the bit towards the end of Alien when the camera bumps into Sigourney Weaver's...well, backside and she turns towards the screen and raises her hand to her mouth as if to say 'oops' before continuing with the scene? I searched for that on YouTube but shockingly it isn't there. Strange because with all the 'blooper' videos on there you'd think it would be there too. And another thing about Alien, at the very start when the camera is panning around the empty ship. Does anyone else hear a noise like something has been knocked over as the camera approaches the two talking helmet thingies? It kinda gives me a bit of a fright whenever I hear it!