Mimic

Trailer for the Director's Cut of the film. 

Del Toro's original sketches reflect his true intentions for the film. Rather than creating simple giant cockroach, monsters to kill the human race, he wanted to create monsters that appeared divine. He saw them as a next step in evolution sent to earth by God to end the human race. Although terrifying in the original concept, these creatures were unlikely to harm children (as depicted by the  child interacting with them) and were kind to people in the sewers who worshipped them as angels. None of these concepts were retained in the final film..