Continuity mistake: When Jack meets his father in the restaurant, his father says that he got a phone call from Karen Walker. When Jack says, "Wow," there is no sign of his arms being crossed, but when it cuts and Jack says, "I got the same phone call," his arms are suddenly crossed.
Continuity mistake: Near the beginning of the episode, Will is pouring some wine. First, he pours a full glass and hands it to Grace, then he begins to pour another glass that obviously already has wine in it. He then hands this to Grace and takes an empty glass from her to fill, which he already filled (there is no sign that she already drank the wine in the glass).
Continuity mistake: The position of the high heels in the barrel, in the church bazaar differ greatly between shots as Karen enters the room, up to when she walks over to find her slingbacks. No-one else touched the shoes in between. They also change position as Karen kindly gives Sally some extra money.
Continuity mistake: After Grace plays Karen's adult video, Karen drops her compact, and powder spills all out of it onto the table. In following shots the powder on the desk changes position and vanishes. In addition the compact case also moves too, and when Karen dropped it onto the table it snapped shut but in a following shot it is open again.
Continuity mistake: When Will and his date are having dinner at Will's flat, will pours his date a glass of wine into an empty glass that the date is holding out. When the shot changes the date is holding a full glass near his chest, and when the shot changes again, Will is still filling it up.