Continuity mistake: It's pretty interesting that Charlotte is supposed to be suffering from a terrible heart condition, yet whenever she's in the hospital, there's never a heart monitor anywhere around.
Continuity mistake: When Charlotte leaves Will's apartment in the white gown he has given her, she is wearing a pair of white high heels. Later, at the party, they're dancing and she is wearing white platform sandals. The next morning, when she wakes up in his apartment and her clothing is strewn all over the floor, the original shoes are seen again.
Continuity mistake: When Charlotte enters Will's building complex for the first time, she's carrying the hat she made for him, and it's raining outside. But later when they leave the building together, the streets are dry. Even the vehicles parked on the sidewalk are immaculate.
Continuity mistake: When they leave her apartment she gets up front, but when the limo lets Will out and circles, she is in the back.
Continuity mistake: When Dr. Tom Grandy is flying in the helicopter, looking over Charlotte's files so that he can operate, what he's actually looking at are the diagnosis sheets found in any emergency room. They're just lists of injuries, diseases, etc.