Stacking/Overlapping/Layering Animations: Spiral Effect
http://pptheaven.mvps.org/tutorials/spiral.html

Tohlz, Shawn
PowerPoint Heaven
2005

Abstract:

I have experimented many ways to create a spiral effect on text. This requires the overlapping technique. The simplest way is to make use of Pinwheel Entrance effect to do the job, while the best way to create the most realistic impact is to have combination of different effects. The drawback on creating spiral effect is that it only works well on high-end computers, while on older computers, you may experience retrograde effect. The best solution is to keep the text small.