I checked out the reviews and summaries from Star Crystal and Alien: sulla terra. The idea of being trapped in a spacecraft and pursued by an alien definitely sound familiar, but I don't remember there being any eggs or morphing of the aliens. Doesn't mean there aren't those aspects in the film, I'm not sure I actually watched the entire thing, but the alien image I remember was a full grown "adult". That and I'm almost 100% certain of the red spaghetti description.
Now that I think about it the alien itself didn't look very scary. Really, how menacing can a big mess of red spaghetti/yarn/playdough be afterall? And I think that was the scary part...the fact that it was very unassuming, with no nasty teeth or claws or anything, and yet it was still devouring people in a very quiet, almost polite manner. It added extra suspense to the movie because you couldn't hear it approaching and I don't remember that it made any noise. I can't even recall how it moved, being a big blob of spaghetti with no discernable legs. I think the only reason that it was able to kill the crew members was because they were stranded in space, with no means of escape...otherwise they could have just outrun the things! Maybe there was some mind control involved, that surely would have made more sense.