This is an interesting 3x3 Creeper piston door, very easy to build, and you'll easily know it by heart after building it once or twice! :-) Please tell me if you'd like a tutorial, or a much more detailed showcasing!

Additional Notes

I did not come up with the design for the middle section of the 3x3 piston door, however I came up with the design for the 3x3 Creeper faced door-part.