No, it's not a penis (I'll post one of those later). It's a Klingon Warbird (Star Trek TOS).

Difficulty : Intermediate
Number of Bills : 1
Denomination Recommended : Any
Credits : Origami with Dollar Bills by Duy Nguyen.

Diagram [PDF] (currently none available)

Top
Klingon Warbird 01-01
Front
Klingon Warbird 01-02
Front Angle
Klingon Warbird 01-03
Rear Angle
Klingon Warbird 01-04