I made this a while ago… the original inspiration was a screensaver I wanted to copy, but the effect went through many iterations so the end-result turned out quite different.
It uses randomly drawn and tweened curves, some BitmapData-action for the blurry smear, and Color.interpolateTransform for the subtle color-changes.
It reminds me of a deep-sea creature of some sort.

Hey great demo, care to share the code?
gimme the code or im gonna decompile this!