Factual error: The "robot guy" is credited as Nigerian but when Stu pays for the broken doll, he speaks Swahili, mostly spoken in East Africa. (00:23:05 - 01:16:40)
Factual error: In one quick shot Stu scans the surrounding buildings looking for the sniper's location. You can see the Grace Building from his point of view. You would not be able to see this building from his location at 53rd. street. The Grace Building is at 42nd & 6th.
Factual error: At the end of the film, the police just let anyone walk around the crime scene: in addition to the caller you also see various tourists gathered around the phone booth. The police would never ever do this: as Leon the pimp was murdered right by the phone booth it is a crime scene and as such must be cordoned off for the forensics team to arrive, instead of letting people contaminate the crime scene. Even though the police "know" the pizza guy did it, they still need to look for forensic evidence.
Factual error: Several times, throughout the movie, Stu or another character using a cell phone is hung-up on. When they are hung-up on, instead of the cell phone dropping, they hear a short dial tone. Actually, when a call is dropped, the cell phone side simply disconnects. You never get a dial tone.
Factual error: The Caller tells Stu that Channels 2 and 5 were coming to see him. This would be correct, since Channel 2 is the CBS affiliate for New York City, and Channel 5 is the FOX affiliate, but the news vans that show up indicate that channels 5 and 8 are covering the stories. The nearest broadcast Channel 8 is in Connecticut. (The only channel 8 in the New York City area is used by a cable station for a premium channel or local programming.)
Factual error: Right after Stu is shot and the police find the dead pizza guy, Stu's wife runs over and embraces/kisses Stu. Moments later while she is still embracing him, the dead pizza guy is wheeled over on a gurney. No way they would have gotten a gurney up, loaded him on and brought him down that fast. Not to mention moving a dead body from a crime scene without any forensics or investigators doing their thing first.
Factual error: The recreation of West 53rd St. is full of mistakes. The street, for example, is mysteriously as wide as an Avenue. The curbs are much higher than they should be, and the buildings are set back much farther from the street than they should be. Studio 54 and the Ed Sullivan Theater should be on the north side of the street, and the back of Roseland should be on the south. There is a subway entrance in the scene that's a block west of where it should be. This is not surprising as the film was shot in Los Angeles, not New York City.
Answer: The pizza man is intended by the Caller to be a decoy so he can get away. The Caller sends the pizza man to the phone booth so that Stu will identify him later in the apartment, giving the police a convenient answer to the mystery while the real Caller escapes. In fact, at the end of the movie, the Caller comes to visit Stu - obviously he's not the dead pizza delivery man.
Phoenix