When Ving Rhames heard of a remake of Dawn of the Dead (1978) was in production, he tracked down producers to be in the film.
For the scene where Ana stitches Kenneth's wounds, the director hired a real nurse for the close-ups. She misunderstood the director's directions to go deeper and inadvertently punctured Ving Rhames' skin and stitched the prosthesis to his arm. He didn't say anything until after the scene was done filming and the director thought the blood was merely "a really good effect".
The two zombies with missing limbs (the jogger missing an arm and the legless zombie in the parking garage) were both played by actual amputees. The same thing was done for one of the first zombies seen in the original Dawn of the Dead (1978).
CJ's elevator line, "I like this song," was improvised. There wasn't even any music playing while they filmed it.
Although he had strong reservations about some elements, George A. Romero professed to be surprisingly impressed with the film.
Zack Snyder: a member of a commando unit (with shades holding an assault weapon) in front of the Capitol Building in Washington, DC. This scene can be seen during the opening credits montage of video/news clips of zombie attacks.