When Vivian and Edward are in the penthouse and Edwards gives Vivian $100, she puts the money down in her boot. After the champagne is delivered to the hotel suite she takes off her boots and the money is nowhere to be seen.
The pancake Vivian is eating was, for most of the scene, a croissant. Director Garry Marshall said he liked the performance she gave in the latter part of the scene better, so the croissant magically becomes a pancake, which she began to eat as they did more takes. While this may be the case, there is still a continuity issue. In the first scene with the pancake, she takes a second bite. In the next scene with the pancake in her hand, there is only one bite missing. Not only that, but the the pancake with one bite missing has a different bite pattern and is clearly a different pancake.
When Vivian finds Edward sleeping, she has a long white nightgown on when she comes in the room. She kisses him and they begin to make love. When Edward pulls her nightgown over her head, it is now a camisole.
When Edward drives up to Vivian's apartment at the end, she quickly pulls the ponytail holder off her hair and messes it up with her hand. But in the next shot, she is standing smiling and her hair is perfectly neat.
When flying from Los Angeles to go to the opera in San Francisco, the plane takes off in broad daylight. As they are ascending, and the pilot comments that it should be a smooth flight, the sun is setting. By the time they land, it is night. You can drive from LA to SF faster than that.
When Vivian is offering Edward a choice of condoms, she is holding four colored condoms (other than the gold circle condom). In one shot, Vivian in holding the condoms in a certain order. In the next shot, they are in a different order and then in the third shot, they are back in the same order as in the first shot.
Near the end of the film when the limo with Vivian pulls away from the curb a Rolls is coming up behind the limo to park in front of the entrance. The shot from within the limo through the rear window during the u-turn never shows the Rolls passing behind the limo. Then it turns right and the entrance of the hotel comes into the shot. When Vivian looks back at the hotel the parking zone is empty.
During the polo match Edward is shown wearing a straight-collar and the tie that Vivian gave to him as a gift, tied with a half-windsor. A later shot shows Edward with a spread-collar and that same tie, but with a full-windsor knot. As the scene progresses, the shot of Edward alternates back and forth between the straight and spread-collar (even with a shot of the spread-collar with a half-windsor knot).
Edward is wearing a vest when they leave the hotel, then in the limo on the way to the Blue Banana, the vest is gone, and then when he confronts the thugs in the alley, he's wearing it again (Garry Marshall said it kept bunching up in the limo scene, so he took it out).
When Philip Stuckey tells Vivian that "this is not a home, this is a hotel room and you're not the little woman," the champagne glass Stuckey holds goes from his right hand to his left hand in between shots as he sits on the couch next to Vivian.
When Vivian is being shown table etiquette by Barney, the Hotel manager. The camera pulls back as if it's on the end of a long boom rather than a dolly. You can tell it's a long boom because of all the up and down shaking which gets worse and worse.
After the tour with the Lotus, they both exit the car in front oft the hotel, where Vivian allegedly starts waiting for the bus. But even though Vivian was the last to drive with the Lotus, she never hands him back the car keys.
When we first see Vivian in bed, she's wearing bikini panties. When she rolls over, the line of an elastic band is visible across her stomach, revealing that Julia Roberts (or her body double) changed from briefs to the fancy underwear just before the scene.
In the last scene when he "rescues" her on the fire escape, camera shots from her window show the ground as being dry even though it has been raining. Shots from the ground looking up at the fire escape show the ground as wet.
At the very beginning of the film, Vivian's right hand can be seen using a black Magic Marker to color in the scuff marks on her boots, however both Vivian and Julia Roberts are left-handed, as can be seen at the end of the film when Vivian is writing in a notepad when Phil arrives.
The use of 2 limousines is not a goof. The gray Cadillac limo in the first part of the film was one leased by Edward for the week. The white Lincoln at the end belongs to the hotel, and the hotel driver took Edward to where he had dropped off Vivian earlier.