Shapeulator is essentially the product of a modular patching session, and a desire to have the core setup used available for further sound design fun. At the most basic level, it is a subtractive synthesizer, with some additional features that make it especially useful for certain types of pads, fx sounds, and synthetic percussion.
The main features that separate Shapeulator from other analog-style subtractive synths are the waveshaper oscillator and resonator. The waveshaper oscillator is a fairly standard VA osc with a waveshaper that is controlled by another oscillator. This second oscillator can be modulated independently, and creates a sound something like amplitude modulation. The resonator is a stereo bank of tuned delays with feedback, which can also be modulated.