Factual error: Considering the brightness of the fusion process, Dr. Octavius has to wear special goggles to be able to see it. Yet no one else in the room is wearing such goggles or seem hurt by watching the whole process, just as at the end of the movie. When welding something, no one can look at the arc that's created, as it would hurt his eyes and burn his retina; presumably, the fusion process would be brighter and more powerful than that, and so should have some kind of damaging effect on everyone's eyesight (except Spider Man's, maybe).
Spider-Man 2 (2004)
Plot summary
Directed by: Sam Raimi
Starring: Kirsten Dunst, James Franco, Alfred Molina, J.K. Simmons, Tobey Maguire, Rosemary Harris
Two years of being Spider-Man is really starting to catch up with Peter Parker. He now attends Empire State University and his alter-ego is starting to cut in on his social life. His powers are also cutting off on him from time to time. He's invited by Harry Osborn, his best friend and new CEO of Oscorp, to attend an experiment conducted by famed Dr. Otto Octavius. The experiment, which was to create the power of the sun, required Octavius to where four mechanical arms his back, but it goes terribly wrong. During the chaos Octavius' wife is killed and the arms malfunction making them stuck to his body and leaving him completely out of control of them. After Peter misses Mary Jane's play she gets mad and tells him that she's getting married to J. Jonah Jameson's son, John. To top things off, Peter finally tells his Aunt May that he was responsibly for Uncle Ben's death, which she doesn't take very well. Meanwhile, Doc Ock is trying to rebuild his machine. So he creates a scene at the bank to get the money he needs for the parts. Thinking that he isn't meant to be Spider-Man, Peter throws away his costume in order to live out a normal life. Without Spider-Man around, crime in the city skyrockets.
More mistakes in Spider-Man 2
Mr. Ditkovich: If promises were crackers, my daughter would be fat.
Trivia: Dr. Curt Connors, Peter's one-armed teacher in the film, is the man who will later become The Lizard, one of Spider-Man's longest running enemies.
Question: How come Harry and Peter stopped living together?
Answer: While it's never mentioned in the film, the most likely explanation is that Harry, as a rich kid, grew tired of "slumming it" and decided to move back into his mansion.
Harry and Peter's relationship quickly turned sour after Peter refused to discuss Spider-Man as Harry felt Peter knew more than he let on. Peter is Spider-Man's "personal photographer," and Harry only wants to avenge the death of his father. It's not unlikely to assume Harry left to live alone because he was angry Peter wouldn't help him find Spider-Man.