strange behavoir of light with Transparent Diffuse Shader

Unity Engine
1

Hi, I noticed a strange behaviour of light with the build-in Transparent/Diffuse shader.
I have attached three screenshots of an enemy object build from several textured planes with diffrent shaders.
SPRITE/Default, Transparent/cutout and Transparent/Diffuse. The first both work as expected.
Its for an 2D game, but i want it to be affected by a lightsource.
Both the build-in Transparent/Diffuse as well as the SPRITES/Diffuse make the object look like all overlapping planes where some kind of additive or semi transparent in the lighted areas.

Can anybody tell me why the Transparent/Diffuse reacts to light this way?

SPRITE/Default and Transparent/cutout:
1491759--83303--$2014-01-21 09_25_05-Unity - 1_1_Tristoy.unity - Game2014 - PC, Mac Linux Standalone_.png1491759--83304--$2014-01-21 09_25_35-Unity - 1_1_Tristoy.unity - Game2014 - PC, Mac Linux Standalone_.png

Transparent/Diffuse (this one behaves strange):
1491759--83302--$2014-01-21 09_24_50-Unity - 1_1_Tristoy.unity - Game2014 - PC, Mac Linux Standalone_.png

2

why does the image look like a cartoon? where are the vertices?