Continuity mistake: The morning after the tsunamis, Little Ethan was at Pilar's house. He came running out of his bedroom and accidentally saw Rachel's corpse. Later, Ethan Winthrop and Gwen came to the house, but left alone. Theresa later left the house, and then Alistair brought her into the Crane mansion with much fanfare. She entered alone, and then went up to see Jane, still alone. But when we next saw her, she was in Jane's bedroom with Little Ethan, even though Little Ethan never left Pilar's house.
Continuity mistake: On 6/24/04, Fox told Whitney that the kitchen at the Sea Cliff Inn had closed for the night. He managed to convince the cook to make a couple of hamburgers for him and Whitney. (This happened offscreen, but they talked about it before and after.) Later that same night, on 7/6/04, Fox and Whitney went with Theresa and Chad to have a full dinner at the hotel's restaurant, hours after the kitchen had supposedly closed for the night.
Continuity mistake: On 7/4/05, Eve says to Julian, "Miles is your grandson, too, even if Chad doesn't know it." Julian is Chad's father, and Chad is the baby's biological father, but Whitney has told everybody that Fox is Miles' father; Eve and Julian know the truth. However, Julian is also Fox's father, so Chad does know that Julian is Miles' grandfather, even if it's for a different reason than he thinks.
Continuity mistake: On 4/30/04, Even and Julian were talking in the park. Eve told Julian not to protect her by confessing falsely to raping her, in part because T.C. would kill him before he could even be put in prison for his other crimes. It was full daylight. The next time we saw them, Julian was making his immediate response to that statement, pointing out that T.C. wouldn't have a chance to get near him. But it was pitch black, even though only a few moments had passed.
Continuity mistake: Early in 2006, when she was planning to become a nun, Whitney whipped herself on the back to punish herself for her sins, injuring herself badly. In December of that year, she got married and wore a gown that revealed much of her back, but there were no scars at all.
Continuity mistake: In late February, Eve confronted Whitney about deliberately malnourishing herself and her baby. Whitney was many months pregnant, but had not gained any weight. The actress is very skinny, and was not wearing a pregnancy pad. Later, around the second week in March, Whitney suddenly had a round belly, since the actress was wearing a small pad. However, it was supposed to be later the same night for all the characters, so her body couldn't have changed like that.
Continuity mistake: On 11/25/03, Ethan says that Gwen confronted Theresa the day after she saw her and Ethan kissing on television. But Gwen actually confronted Theresa later the same night. In fact, it is still impossibly late that same night when Ethan makes this statement.
Continuity mistake: At the end of the 5/24/04 episode, Luis put Sheridan into the back seat of his car and drove off with her while she insisted that she didn't want to go. At the beginning of the 5/25/04 episode, Sheridan was sitting in the front, still insisting that Luis take her home. But how did she get into the front seat?
Continuity mistake: In every single scene that Theresa appeared in for an entire week in October, 2003, some member of the hospital staff was telling her to leave the premises immediately. She was told "for the last time" at least six times, and Dr. Taylor said twice that he was going to call security. Yet Theresa stayed at the hospital without anybody actually doing anything about it, and she managed to exacerbate Gwen's condition three separate times.
Continuity mistake: Several times during the tsunamis, in the week of 8/1/05, Sam Bennett's shirt would switch between being yellow to a light orange from shot to shot. The orange shirt was distinctly darker than the yellow one, even when both were soaking wet. Actor James Hyde was wearing the yellow shirt, but his stunt double had the orange one.
Continuity mistake: When the show started in July of 1999, Gwen Hotchkiss and Sheridan Crane barely knew each other. When Gwen and Ethan were on the beach in Harmony, Gwen asked Ethan many questions about Sheridan. Later, when Gwen and Sheridan met in Paris, Sheridan asked Gwen a lot about her relationship with Ethan. Both exchanges made it clear that Gwen and Sheridan were not well acquainted. However, years later, Gwen and Sheridan often spoke about having been lifelong friends, even though they had only known each other for a few years.
Continuity mistake: Throughout 2000-2001, the character of Ethan Crane was said to have three sisters who were all away at boarding school. By 2003, he instead had just two still-absent sisters, and a brother, Fox, who now appears on the show. (By siblings, I mean children who were raised as Julian and Ivy's.)
Continuity mistake: On 2/1/05, at the beginning of the episode, Gwen cornered Theresa and tried to stab her with scissors. Theresa was in her wheelchair, backed up against a wall, and Gwen was standing right over her. Gwen swung her arm, and a wet thud was heard. Then it went to the credits. When it came back, there was a medical supply cart between them, and Theresa was using it to fend Gwen off. But the cart hadn't been seen before, and would have needed to already be between Gwen and Theresa in the last wide shot in order for Theresa to use it like she did just a few seconds later.
Continuity mistake: On 6/24/05, Sam and Luis were trying to break through a wall in the Crane mansion. The sound of metal on metal is heard, and Pilar asks what has happened. Luis and Sam explain that they've just hit a metal barrier that they think must conceal the room they're looking for. But several square feet of metal are already exposed. Why wasn't the metallic sound heard earlier, and why is everyone acting like they've only just discovered this second barrier?
Continuity mistake: On 10/19/04, Fox refers to Ethan as his "oldest half-brother," but in reality Chad is his oldest half-brother. Fox is specifically thinking about all the changes to his family, and everyone knows that Julian was with Eve before he married Ivy, so it's a no-brainer that Chad is older than Ethan.