Just after the DVD is inserted into the player, and immediately after the Touchstone logo, a dark, fuzzy image appears in black and white, very quickly. It is a movie still, with Merrill, Morgan, and Bo sitting on the couch with the aluminum hats on their heads. The picture is shown even faster when "Play" is selected.
The "Brazilian Video" was shot in Miami, but the children were all Brazilians. A Portuguese couple was also brought to play their parents, but M. Night Shyamalan decided not use them, because he noticed that their accent was totally different.
The film was shot on the property of an agricultural school, Delaware Valley College, where two areas of corn were already growing at different stages. The corn grown for the film was naturally further behind the other two areas of corn, so it was not a planned element.
M. Night Shyamalan didn't want the trailers to make any reference to The Sixth Sense (1999) because he felt it didn't trust what was to come next. That it didn't give the film its own life, and audiences would assume Signs was exactly the same type of film as The Sixth Sense.
Only the scenes in the bookstore and the pizza shop were filmed in Newtown (Bucks County), Pennsylvania. The scenes of the house and cornfields were filmed on forty acres, that were leased to the film company by Delaware Valley College (an agriculture college) of Doylestown (Bucks County), Pennsylvania. After filming, the film company donated all the corn grown to the college's vegetable and fruit market. The house was built on the grounds and torn down after filming. Delaware Valley College is acknowledged in the credits at the end of the film. The drugstore scene was filmed in Morrisville (Bucks County), Pennsylvania.
The prints hanging over the fireplace and Graham's bed in the Hess's home are "Stone City" and "Spring Plowing," respectively, by American artist Grant Wood (1891-1942), who is perhaps best-known for his painting "American Gothic." He co-founded an art colony in Stone City, Iowa in the early 1930s.
3 out 4 of the Hess family members are played by actors or actresses who are the younger siblings of actors. Rory Culkin, Abigail Breslin, and Joaquin Phoenix are respectively related to Macaulay and Kieran Culkin, Spencer Breslin, and the late River Phoenix.
One of the opening scenes shows the cornfield, swing set, and table at night through a pane of glass; crickets can be heard softly chirping as the camera pans backward into the bedroom. Suddenly, they stop chirping and Rev. Hess awakes, startled. The crickets motif is used several times in the film to lend an eerie air to the scene, much as the unnatural cawing in The Birds. Anyone who lives in the countryside or has gone camping is familiar with the cricket. They are the "alarms" of the forest - they "hear" vibrations, so when someone...or something...approaches, they go quiet. Their chirping is an "all's well!"; when they go quiet, you know that danger may be near...
Although M. Night Shyamalan uses the motif of water to convey weakness of a character, and his character tells Rev. Hess that he's planning to go to the lake, because "it is known that they don't like water...", it's also a nod to other films in the sci-fi genre: the classic 1963 "The Day of the Triffids", in which carnivorous aliens feed on humans - and having been hit unsuccessfully with fire, chemical and other weapons - are finally vanquished by the simplest of elements - seawater! And, the more recent 1988 "Alien Nation", in which seawater behaves as an acid on the aliens' flesh and dissolves them, painfully. Or, as some would say, they were "liquidated".
The aliens were originally scripted as having feminine builds and movements, thus the movements of tall, thin actresses were used as models for CGI tests, and some shots ("Brazilian Video"). However, it was decided that female bodies did not convey a threatening enough posture for the creatures, and a male CGI stand-in ended up being used in the final scene with Morgan, as well as on the rooftop.
The script originally called for the aliens to have a camouflaging ability, much like the one used by the Predator in the Predator franchise. However, when M. Night Shyamalan's saw the ILM test shots of the creatures, he decided that it was too effects-heavy.