Most of the time in the Alien scene of the Great Movie Ride, guests are looking around waiting for the terrifying creature that waits to claim its next victim. But hidden in this scene is a little reference to the original Alien film.
On the right side of the attraction as you enter the Alien scene just after the windows that look to the starfield, there's a space suit and a little drinking bird with a glass.
So why is there a bobbing bird that "drinks" from a cup? If you remember the opening montage from Alien, there's a shot from the Nostromo that does show a drinking bird on a table.
We all know how much Imagineers love to pay attention to the fine details in their story telling and this is another great example of how they use something so small and subtle to help build credibility and believability that you are indeed in the film.
I'll even go one step further and say that if you watch the opening scene (I'd post a video but there's no copies available online), the film begins with a montage of the camera walking through the inside of the Nostromo. You see these drinking birds briefly as the camera pans to the left and continues its tour of the ship. On the ride, you see the drinking bird briefly before moving to the left and moving deeper into the scene. I don't believe that's a coincidence.