The poo monster was actually a black bin bag.
In the scene where Mike Matei's character is mixing chemicals for a science experiment, the majority of the substances and bottles on the table are just beer.
The shot of the fecal monster climbing up a monument building was filmed with cardboard cutouts turned upside down. The fecal combination was poured over the miniature, which was then flipped in post-production.
The fecal matter was created using peanut butter.