I wrote this Java applet probably somewhere in 1997. The bouncing ball is a pre-rendered image. The top 2/3 of the image is copied up-side down in the bottom part of the applet to create the mirror effect. The wall is an image, and is based on the actual kitchen wall I had in those days. The bench is another image with "holes" in it (transparency) which is put on top of the mirrored image. This creates the illusion of splashes of water reflecting the animation. All three images were rendered using the Persistence of Vision Raytracer.
Another mirror animation predating this one is also available: Mirror animation.