David Seltzer's name was attached to the initial promos for the movie. For an unknown reason, it had been removed by the time the film went into general release.
The improvised explosive Margo makes using two jars is very similar to the one made by Jean-Claude Van Damme's character in Sudden Death (1995), director Peter Hyams' previous film.
The two sniffer dogs used to track down the creature in the sewer system are called "Castor" and "Pollux", sharing their names with the Troy Brothers from John Woo's Face/Off (1997), which in turn are named after the Dioscuri from Roman/Greek mythology.
The tank into which Margo falls only contains hot water, used to loosen skin from a carcass. At the time she enters this tank, it is switched off and the water is cold.