Making gif's in Gimp is pretty easy. I don't know what basilico used, but for Gimp just copy a layer, stack it, modify that layer slightly, and repeat. Gimp also has a great animation plugin. You can even optimize it (to reduce duplication on stacked layers).

If you need me to edit this pic, I can. It was a coin flipper whether or not to post it. There's a lot of tail in that pic, and coincidentally, so was the coin when I looked at it.