Judy Garland found it difficult to be afraid of Margaret Hamilton, because she was such a nice lady off-camera.

When the wardrobe department was looking for a coat for Frank Morgan (Professor Marvel/The Wizard), it decided it wanted one that looked like it had once been elegant but had since "gone to seed". They visited a second-hand store and purchased an entire rack of coats, from which Morgan, the head of the wardrobe department and director Victor Fleming, chose one they felt gave off the perfect appearance of "shabby gentility". One day, while he was on set in it, he idly turned out one of the pockets and discovered a label indicating that it had been made for L. Frank Baum. Mary Mayer, a unit publicist for the film, contacted the tailor and Baum's widow, who both verified that it had at one time been owned by the author of the original "Wizard of Oz" books. After the filming was completed, it was presented to Mrs. Baum.

Many shots were trimmed down or edited out of the film because they were too intense for families and children. In particular, one deleted shot shows the tornado completely enveloping the farmhouse. Also, later in the film a lot of The Wicked Witch of the West's scenes were either trimmed or deleted entirely, as Margaret Hamilton's performance was thought to be too frightening for audiences.

Margaret Hamilton, a single mother, got into an argument with the studio over guaranteed time to work, only agreeing to take the role of the Wicked Witch three days before filming. Ironically, although she finally got an agreement for five weeks of work, she ended up working on the film for three months.

Margaret Hamilton, a lifelong fan of the "Oz" books, was ecstatic when she learned the producers were considering her for a part in the film. When she phoned her agent to find out what role she was up for, her agent simply replied, "The witch, who else?"

Continuity

When Dorothy firsts meets the Scarecrow, her pigtails change from short and curly to long and straight several times.

After escaping from Miss Gulch's basket, Toto returns to Dorothy's room by jumping through the rectangular opening where there should be a windowpane. Soon after, the twister blows the window out (that wasn't there when Toto came back) and knocks Dorothy unconscious.

When the group is asking the guard if they can see the Wizard, his mustache suddenly goes from being pointed upward to downward between shots. This is the result of a deleted scene.

As Dorothy and Toto run down the dirt road toward home at the beginning of the film, Dorothy bends down to pick Toto up and you can see a grease spot on the front of her dress, but by the time they reach home, it has disappeared.

When Glinda is leaving Munchkinland, all three members of the Lollipop Guild and a female munchkin (among others) run toward her pink bubble and shout their goodbyes to her. They are still standing behind Dorothy in the very next shot as she says, "People come and go so quickly here."



Factual errors

The Wizard tells the Scarecrow, "Why, anybody can have a brain. That's a very mediocre commodity! Every pusillanimous creature that crawls on the earth or slinks through slimy seas has a brain!" He's right about the earth-crawlers, but the sea contains many creatures without brains, including jellyfish, corals, Portuguese man o' war, starfish, clams, oysters, sea cucumbers, sea urchins, sea sponges, sea lilies, sea anemones, and sea squirts.



Incorrectly regarded as goofs

The Wizard states that he is "an old Kansas man" yet his balloon is registered to Omaha, Nebraska. Midwestern carnival performers often travel between two or three states on a regular route.

Tin doesn't rust. However, the movie takes place in a fantasy world, where it can do so if the filmmakers say it can.

When Dorothy is in her bedroom at the beginning of the movie the windows are closed with the curtains on them. The twister blows 'both' windows out and the one hits her on the head causing her to pass out. In all the next shots of her in the bedroom, the right hand window with the curtain is back in the shot. It should not be there as it was blown out. However, this ignores that the movie presents the happenings in OZ as a dream Dorothy had after being knocked unconscious. Therefore, in her dream, the farmhouse is undamaged and not a goof at all. This could also explain many of the so-called goofs during telling of the OZ events.

When the group enters the castle disguised as Winkies, the Tin Man is carrying a spear. His axe reappears seemingly from nowhere to smash the door open to free Dorothy. The Winkie costume was very bulky with more than sufficient room to conceal the axe.

Glinda tells Dorothy never to let the ruby slippers off her feet, but apparently the slippers remain stuck to Dorothy's feet after the Witch of the West claims they can't come off while Dorothy lives. Obviously this kind of speech is part of Glinda's effervescent character.



Revealing mistakes

During the apple tree sequence, Dorothy's slippers momentarily disappear (she is wearing black patent leather shoes). This happens when the tree throws an apple that makes Scarecrow fall over. The black shoes are visible bottom right, just as Scarecrow lands on his bottom.

The purple "Horse of a Different Color" can be seen licking off his purple dye, which was made of grape-flavored gelatin powder.

When the Witch is melting, the outline of the trap door is visible under her dress.

When the Wicked Witch of the West disappears from Munchkinland in a cloud of smoke and fire, the smoke appears before she reaches her mark.

After the scarecrow was re-stuffed because of his body being severed by the monkeys, he stands up, and trips slightly in the hole that was meant to conceal the lower half of his body.



Audio/visual unsynchronised

After saying, "Well, my little pretty, I can cause accidents too," the Witch says something else which we do not hear. The script backs up this claim. The additional dialog was, "And this is how I do it!" Margaret Hamilton's lips can be seen forming the words "And this" without sound before the shot cuts away.

When Dorothy uses the knocker on one of the Emerald City doors, four knocks are heard although she only hits the door three times. The first one is heard while she is drawing the knocker back.

The Mayor and his agents' voices get mismatched in at least two places. During the congratulatory music, a "lawyer Munchkin" interrupts the festivities and demands legal verification of the Witch's death. When they exchange words saying, "From now on you'll be history! You'll be hist - you'll be hist - you'll be history!", the "lawyer" Munchkin has a completely different voice, as though from a different actor. Furthermore, when the Mayor says that last "history!", we hear the "lawyer" Munchkin's voice instead.

The real wizard makes the fake wizard's voice by talking directly into the microphone, but when the fake wizard says "Pay no attention to that man behind the curtain!" the real wizard is pulling back the curtain, pointed away from the microphone and not talking at all.

When the group chants, "Lions and tigers and bears!". just before encountering the Cowardly Lion, and it is Dorothy's turn to say the first, "Oh my!", her mouth does not move.



Crew or equipment visible

In the close-up of the Palace Guard crying, tears can be seen dripping from a device attached in his false eyebrow.

A flesh-colored hand is visible in the upper left-hand corner of the frame in the closeup of the Witch being splashed in the face with water. The Scarecrow is wearing dark burlap gloves, the Winkies are wearing black gloves, and Dorothy is holding the bucket, so the only explanation is that the hand belongs to a crew member throwing water on the Witch.

The cameraman's shadow is visible as it pans across the Sleepyhead Munchkins' nest in Munchkinland.

Studio lights are reflected in Dorothy's bedroom window as it blows out of its frame and knocks her unconscious.

When we first see Munchkinland, you can see the shadow of the camera pass over in one of the establishing shots.



Errors in geography

The twister seems to teleport between shots. this can be seen when it's behind the farmhouse but then jumps miles away and changes position. This can also be seen when Dorothy is entering through the gate and it's about 50 meters away from the farmhouse but when we see the adults closing the storm cellar door it's now back where it was when Aunt Em was calling for Dorothy.



Plot holes

When the Witch sends out the flying monkeys, she says, "I've sent a little insect on ahead to take the fight out of them." Those "insects" are Jitterbugs. The Jitterbug scene was filmed, but later cut. The line, however, was not removed.

When Professor Marvel looks into the crystal ball, he mentions a weathervane which is not visible in any shots of the farmhouse.

Miss Gulch is not brought up in the final scene, leaving her threat to have Toto put down unresolved.

It's never explained how/why the ruby slippers transfer from the Wicked Witch of the East's feet to Dorothy's.



Boom mic visible

When Dorothy is balancing on the pigpen fence, you can see a boom shadow pass over the scene.



Character error

After the Wizard gives the Scarecrow his diploma, he says, "The sum of the square roots of any 2 sides of an isosceles triangle is equal to the square root of the remaining side." This is a misstatement of the Pythagorean Theorem, which is, in fact, about right triangles and not isosceles ones. However, this statement is not true about any triangle, and so it is completely wrong.

Dorothy smiles and tries not to laugh after she smacks the Lion and he asks, "Is my nose bleeding?" Judy Garland buries her face in Toto to conceal this.

A Munchkin runs up to Judy Garland and shouts 'Judy' instead of 'Dorothy'.

During the "If I Were King of the Forest" song, the Lion asks, "What makes the Sphinx the seventh wonder?" The Great Pyramid, not the Sphinx, is one of the seven wonders of the world.

In the "King of the Forest" scene, Dorothy trips on the emerald carpet on her way back up the stairs.