photo: Tomas Rawski via Creative Commons (flickr)
Shadow reveals only when light source lightens the object. Although the shadow resembles an object, it means(infers) an opposite side of the object, either good or bad.
Thus, I want to project the shadow on the pavement The shadow is the opposite side of the object like reflection.
This requires the following techniques and devices;
3D software - Maya
projector -
battery - DC12V link
power inverter
cart
The contents of the shadow can be;
pictogram + sarcastic phrases
Sarcastic phrases may be direct and understood easily (even it's the role of sarcasm!).
Therefore, one option is the mix of pictogram and phrases that looks like something else.
Still phrases difficult to realize its meaning are good good option.