In the first scene at Elaine's, as Isaac is beginning to say something, two people (presumably customers of the restaurant, as it was running while they were shooting) walk in front of the camera. Isaac laughs, and quickly recovers with an impromptu remark about how his girlfriend has to go and do homework.
Camera and crew reflected on passing cars while following Isaac running down the street.
During the fireworks in the opening sequence the screen goes black several times - but not completely: Two bright circles - glasses - can be seen as a reflection (probably because the sequence was filmed from behind a window) and there is also a very slight after-image of the person wearing the glasses who might even be the director.
When Isaac asks Tracy how old he will be when she is thirty-six, she says "sixty-three," and he agrees. Earlier Isaac says that she is seventeen and he is forty-two, which means he is 25 years older than her, and would therefore be sixty-one, not sixty-three.
It seems inconceivable that both Jill and her editor did not know that writing about her and Isaac's marriage in her book would set herself up for a libel and defamation lawsuit, as Isaac (Woody Allen) was a private citizen and his privacy rights were grossly violated.
Mary (Diane Keaton) is supposed to be an intellectual, but when she says the name Diane Arbus, she mispronounces it, saying "Diane" the same way you would say Diane Keaton. Diane Arbus' first name is pronounced "Dee-Ann".