Goofs

Ater the fight at the dance, a shot shows Sharon and Susan on the ground, covered in food. Susan's dress, which Sharon had cut the back out with scissors earlier, is brand new, as if it had never been cut.

In the isolation cabin, whilst the twins are getting acquainted, Susan's shoes change from white sneakers to blue flats (that Sharon had been wearing).

When Vicky and Edna exit Mitch's house, they get into a 1959 Lincoln 4-door. However when they are driving away, (interior shots of) the car in which they are riding is a 1959 Mercury. This is evident by the distinctive types of rear roof pillars that the cars have.

When Vicky is offered the canteen of water with the lizard perched on top, the canteen lid is open. When Vicky throws the canteen back, the lid is on.

At the isolation cabin, just after the rainfall, Sharon and Susan go outside and the cabin exterior and grounds are dry. They then go back inside and figure out they are twins. Sharon momentarily goes back outside and the cabin exterior is wet, as expected after a strong rainfall.

When Mitch and Maggie are kissing in the kitchen, and Maggie is stroking his face, she is clearly wearing a diamond wedding set on her left ring finger. At that point in the story, the couple has been divorced for 12 years, Maggie had not re married, and they are just then reconciling, so she wouldn't have any reason to be wearing a diamond ring just yet.

When Hecky told Vicki that the 2 Little bear cubs wouldn't hurt a fly, while that statement is partially true, he forgot to consider the fact that their mother bear would've attacked Vicki and possibly the people in the camp if she was present. So Vicki was right to scare off 2 bears which saved her life and everybody in camp.

When the girls are camping by the lake and are offered more trout for dinner, in one scene one of the girls is almost lying on her side, the scene cuts to another angle and she's sitting in the "W" position, then the scene cuts back to the previous angle, she's lying on her side again.

At the golf course, Mitch sits down with his daughter to have a daughter/father chat. He tells her that this place is as good as any. No it is not. It is a fairway, not a park. There would be a group of other golfers, hitting the ball at over 100mph, straight at them.

Sharon exited the plane and walked to the exit area and looked around for her father, who showed up a couple of seconds later and walked Sharon to the baggage area. Sharon is only 13. She is an unaccompanied minor. The airline must maintain custody of her and deliver her to father.

While singing "Let's Get Together," twice Sharon's hand momentarily disappears crossing over into Susan's frame.

Obvious body double for Susan when the table collapses as she and Sharon cat-fight at summer camp.

During a close-up shot of both twins with food smeared over their faces, it is obvious that one girl with the short hair is not Hayley Mills, even under all the goop, but Hayley Mills' double Susan Henning as Susan's eye color was of a brighter shade of blue than Hayley's.

In the isolation cabin, when the window blows open and the girls try to close it, the stand-in's face is revealed.

When Sharon and Susan are singing "Let's get together" you can see that Sharon is not pressing down on the piano keys.

When Susan offered Sharon a fig newton, the fig newtons were in disarray. But when Susan returned the box to the shelf. The fig newtons were in 2 straight lines. Just like they were packaged.

Just past 1:09, Susan reveals herself to her mother and grandmother. She speaks a frequent dialogue mistake saying, "I miss not having a mother". She should have said, "I regret not having a mother", or something else that doesn't contradict the situation.

When mother and daughter are walking in the park the rear projected footage is receding at a pace that is faster than they appear to be walking.

In the opening, Hayley Mills is two names.

When Susan is supposedly playing the guitar, her fingers aren't moving.

While performing "Let's Get Together" with Sharon, Susan plays an acoustic guitar, but the sound it makes is distinctly that of an electric guitar.

When the twins' mother (Maureen O'Hara) is singing the song that was played on her first date with their father, her lips do not match the words that are being sung.

When Maggie descends the outdoor stairs, they are visually made of stone or stucco, but the sound is that of hollow, wooden steps.

Vicky is tricked into going on the camping trip at the last minute, with no time to pack any bags or gear. Yet when they get to the campsite, she has curlers to wear to bed.

In the beginning of the film Ursala tells Sharon that she is lucky because Betsy mom sends her candy every week. The problem is the camp just got started for the summer, so the camp was not open a couple of weeks ago.

Soon after Sharon arrives at Susan's home (pretending to be Susan), Verbena says something about washing all of Susan's dirty camp clothes, but is seen putting many of them directly into the dressers in Susan's room without washing them first.

Susan's accent is inconsistent throughout the film - sometimes she (almost) sounds American, while most of the time she has the same British accent as Sharon. Growing up in California, with an American father, there's no reason she'd ever sound British.

Sharon grew up in Boston, among the "society" crowd. IF she was an equestrian, which isn't likely given that she lives in a city, she certainly would ride English style. Yet she very capably rides Western and knows how to care for Susan's horse while the girls have switched places.