Continuity mistake: As the nurse is talking to Susan about the operation, the folding of the paper the nurse is holding on the clipboard changes between shots. First it is half folded over, the next shot it has been folded right over and is being held right down. After this shot it changes again and is now folded back without her moving the paper.
Audio problem: As Carlos is giving his speech at the barbecue, Julie sees Zach and says to Susan "Oh God". After cutting to a shot of Zach and his father it shows Julie and Susan again. If you look to the right of the shot you will see Carlos' face is just looking in front of him and not speaking, but you can still hear him giving his speech whilst he is in shot.
Continuity mistake: When Bree Van De Kamp is sitting on the couch talking to her marriage counselor, as she is doing so she picks up her purse and puts it on her lap, crossing her hands over it. When the camera switches back to her a second later the purse is back on the couch beside her in the exact position it was in before she picked it up.
Continuity mistake: When Orson is on the phone with his lawyer, he sets down the notepad with a page half filled with writing at the front. However, later in the scene Edie walks into the room and the front page of the notepad is full of writing, plus there's an extra line in the first paragraph. No one was around to move the page as Orson was in the shower.
Continuity mistake: During the scene where Gaby and John are in her bedroom talking, she takes a drag from her cigarette while John asks why she isn't happy, but never exhales the smoke from that drag. 23 seconds pass from that drag to the next one and she's in frame the entire time (it cuts between shots of the two of them together and Gaby's close-ups, but doesn't cut away from her). It's also worth noting that Gaby is never seen smoking again at any other point in the series and no explanation is given as to why.
Continuity mistake: Adam hands Katherine the note he found on the floor written by her aunt in a previous episode. Katherine is holding the paper up. When Adam walks around her in the next shot, the paper is gone and Katherine is only holding her keys/purse. The close up of Katherine (the very next shot) shows her holding the paper again.
Factual error: Lynette's neighbor tells her that the pot Lynette's sons gave her is really hers, the neighbor's, and she bought it in Costa Rica. She turns the pot over to show Lynette that the price is marked on the bottom, with a number followed by the letter p. One supposes that the p might stand for peso, except that the currency of Costa Rica is the colon, which consists of 100 centavos. No p in sight.
Audio problem: When Susan suspects someone might be in the house, the seduction music she has put on for Mike is drowned out by the score. When she accidentally hits Mike across the face, the score stops, but the music that was playing in the background has gone. The song in the background before now was music within the show, and it was loud enough to be heard around the house, so we should still be able to hear it.
Plot hole: In season one, Helen said that John turned eighteen last week. And Zach said in season three that he is two months older than John. But in another episode in season three, Lynette said that Zach turned eighteen a month ago. So Zach is two months older than John, and John turned eighteen in season one, but Zach turned eighteen in season three. Season one quote: "Last week he turned eighteen"(they're talking about John in episode "Your Fault.") Season three, quote one: "I'm two months older than John Rowland"(Zach says it in episode "Not While I'm Around.") Season three, quote two: "Until he turned 18, a month ago"(they talk about Zach in episode "Come Play Wiz Me.")