The original image is 90 frames and 70+ kbs. A classic, made using one of the first animation programs. Noted here in the comment tag of this animation

Comment: GifBuilder 0.3.2 by Yves Piguet

The other images are versions of the original that have been optimized or re-built with a few frames. They range from 25kb's down to 4kb's
Image Info Original.. Image Info 1ff1 19kb
Image Info 1ff4 4kb
Another Smooth Animation.txt
Moonlite Dancers ... 36k version
This page is a study of two finely crafted animations using older animation programs. Some of the first animation programs available. I do not know the person/s who made these original images. More than likely the fireflies and the moonlitedancerz were made by 2 different people. Beautiful aren't they!
Looking for information / tutorials about animation?
You will find that info at 2 general locations.my site. Here with the glitter tiles Glitter Methods Overview
and here at My-ImageMagick Tutorials My Morphimation pages could be helpful