Give me a strange little creature in the background of a space film and I am immediately willing to believe it has a very busy life. The main characters may be dealing with the fate of the galaxy. I would also like to know whether the person with four eyes near the door has finished their shift.
Imagine the alien who appears for three seconds carrying a box. What is in the box? Is this a routine delivery? Has the dramatic music made them late? There is a whole smaller film available in which the galactic emergency is an annoying obstacle between one tired courier and a perfectly ordinary evening meal.
Inventing that sort of nonsense is part of the fun of a busy fictional world. A crowded scene gives you people who seem to belong somewhere beyond the edge of the camera. The more seriously the main plot takes itself, the more appealing it becomes to imagine that somebody nearby is mostly concerned about finding a chair.
I do not need an official series about every passing creature. I am quite happy to supply a daft explanation myself. The box contains replacement spoons, the courier is called Colin, and the entire crisis has made the delivery paperwork considerably more complicated. There we go. Another corner of the galaxy accounted for.
