P.S: Anything recognizable is property of Gaslamp Games, who I wanna cover with kisses for making this addictive and fun game!
Here's the DoD site: http://www.dungeonsofdredmor.com/
Step 1: Basic diggleology
You can select which colours you want. Basically we will need two shades of the same colour.
The parts that will need making are:
3) 2 arm fins
4) 2 leg fins (though these could be the same as the arm ones)
Now, the in-game version of a diggle looks much like a potato with a giant ice cream cone stuck to its face, I'll go with the art provided by Gaslamp Games for the t-shirt design. In the pictures, you can find the approximate proportions, based on the t-shirt image. All the body parts are measured in reference to the size of the head, except for the bill and the width of the fins. I will be doing my measurements in cm, but you can do it however you like :)