standard_surface.thin_film can also be used to create a bubble shading effect.
This tutorial shows how to shade the swirling rainbow color effect on a soap bubble. It can be achieved using a fluidTexture2DShape. This scene file consists of a fluidTexture2DShape that is connected to the Specular Color of a Standard Surface shader.
The scene can be downloaded here.
fluidTexture2DShape connected to Specular Color
You must play through the animation time slider in order to see the fluidTexture2D effect.
Thanks to Duncan Brinsmead for his original fluidTexture2DShape texture.