Continuity mistake: Goldie Hawn and Meryl Streep are fighting over Bruce Willis. Goldie Hawn is wearing a tight shirt and tight pants. Meryl is wearing a shirt with a skirt thingy attached and tight pants. Goldie has a hole through the middle of her abdomen where Streep has shot her earlier. They both grab shovels and start fighting. Bruce Willis starts to walk upstairs and he looks over the side and sees the shadows of the two women fighting. The hole is supposed to be on the shadow with the tight pants which is Goldie. Instead, the hole is shown on the body with the skirt attached to the shirt, which is Meryl. (01:10:20)
Continuity mistake: When Madeline is given the card with address of Lisle Von Rhoman on it, she tears it down the middle into two, and the two pieces she tears are torn neatly and straight down the middle. Yet later, when Madeline takes the two pieces of the card from her bag, they are torn much differently, and aren't torn straight and neatly. (00:19:45 - 00:28:20)
Continuity mistake: When Ernest is scared of seeing Madeline alive after dropping down the stairs the cord connecting the phone to the wall suddenly disappears (probably deliberate so he doesn't trip over it).
Continuity mistake: After Ernest pushes Madeline down the stairs, he walks down to her and we see her laying down, with her legs in a 180 degree position. When Ernest talks on the phone to Helen, she moves her one leg, which is now directly in front of her. The camera has been on her the whole time in the background, so there is no way her leg could have been moved.
Continuity mistake: At the book signing Helen kisses Madeline on the cheek and leaves a bright red lipstick mark. She appears to kiss her quite close to the ear but in the next shot, the lipstick mark is more in the center of her cheek.