Personale o equipaggiamento visibile: In the opening bathroom scene, reflected in the convex mirror that Karen bumps.
Errors made by characters (possibly deliberate errors by the filmmakers): Karen teaches her child the French "le table" in stead of "la table".
Revealing mistakes: In the scene right before Karen screams about the pillow being washed, the little girl and her father are sitting at the table eating breakfast. The little girl tells her father that she doesn't like bananas. You can clearly tell that the little girl messed up and said something else causing her to laugh and break out of character.
Continuity: In the rape scene you can see Julie wearing a flesh colored leotard.
Revealing mistakes: When Doob's second victim is lying dead on the table, as one of the cops walks pass her you can see her blinking.