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Before the helicopter crash in the flashback, Marley gives Sam (when she was a puppy) to Neville saying, "Sam, you protect Daddy", "foreshadowing" when Sam actually saves him from infected dogs.
Will Smith grew so enamored of his canine co-star, Abbey, that he tried to adopt her when filming was finished, but the dog's trainer could not be persuaded to give her up.
When Dr. Robert Neville sees the mannequin he calls "Fred" outside on the street, it looks like the mannequin moves its head a little. During that scene, a mime replaced the mannequin to try and play with people's minds when they watched that scene.
The trainer put a piece of tape on Abbey's paw to make her limp, after Sam gets injured fighting the infected dogs.
When he was in pre-production on this movie, Director Francis Lawrence found himself watching The Pianist (2002) with the sound off in order to not disturb his sleeping baby, and he found the quiet effect was extremely moving. He then made stark silence, with limited ambient effects or musical cues, a major part of this movie's process.
The screams and unearthly sounds of the infected creatures in this movie were by Mike Patton, vocalist in Faith No More, "Fantomas" and Mr. Bungle.