Adrien Brody really had braces put on his teeth for his role as Harry, rather than get fake ones put in every day. He realized this was a mistake when he realized that he couldn't get into a fight at a bar because his upper lip would be destroyed by the braces.
Adrien Brody was asked to sign a document clearing director 'Richard Shepard' and producers from lawsuits if Brody's teeth were damaged from the braces he wore during filming. Brody refused to sign, claiming he didn't want to sue anyone, but if his teeth were ruined during filming, he would have to sue.
Both Maura Tierney and Adrien Brody had to rush to finish this movie because both had other, bigger movies to film; Forces of Nature (1999) and Summer of Sam (1999), respectively.
Adrien Brody's parents can be seen as Brody (as Harry) walks away from Maura Tierney and the car crash.