In the scene where Marla is trying out in the gym and she hits the ball though the window you can tell that the ball is going though two different windows. The first shot is from inside the gym and the ball breaks through the window at the corner of the building in a direction towards the corner of the building. The next shot is from outside the building and the ball is not coming out of the corner window, but the window next to it, and not in the same direction as the ball was hit from inside the building. The angle at which the ball came out of the building would never be possible from where Marla was hitting the ball.
After the final game of the championship series, Jimmy Dugan tells Dottie Hinson he has an offer to manage the next season in Wichita, to which she replies, "Triple A." The AAA designation did not exist until 1946; before then, the top minor leagues had a AA designation.
When Kit gets so upset with Dottie for telling Jimmy she was gassed in the last inning, Dottie rationalizes with, "It was an important game, we made the playoffs with this win." There are four teams in the league. All four would have made a playoff format, otherwise she would have said, "We're in the World Series now."
The shoulder patch worn by the postal employee that delivers the letter to Marla was not used until 1965. The film takes place in the 1940s. Letter carriers didn't wear shoulder patches until the mid-1950s.
In the Suds Bucket road house, on more than one occasion, you see a neon sign in the background for Augsburger Beer. Augsburger Beer was not produced until 1959. (Augsburger was originally produced by the Monarch Brewing Co. from 1959 to 1967, and then was brewed by the Potosi Brewing Co. Huber, located in Monroe, bought the brand in 1971 and made the beer until Stroh bought the label in the late 1980s.) The sign appears to be that of 1980's vintage.
During the tryout montage scene, we see a group of elderly women complaining on a broadcast on radio station WMGM. However, that station didn't go on the air for the first time until 1948, five years after the movie was set. Furthermore, WMGM was in New York City.
When Jimmy Dugan walks in to the locker room and urinates, he urinates into a trough which would not have standing water in it, but we hear the sound of someone urinating into a toilet with water in it.
During the scene where Dottie's parents are listening to Maida Gillespie's radio broadcast, you can see in their magazine collection the Life magazine on which Dottie is on the cover doing the splits while catching the pop fly. That doesn't happen until later in the movie.
When all the girls must find their names on the list, we see Doris and Mae hugging each other because they both made the team. In the next shot, while Kit is pushing through the crowd to tell Dottie she had made it, she pushes by Doris who is still waiting to see the list.
When the girls are at the Suds Bucket roadhouse we can see Ellen Sue on the floor dancing. When they cut away to show a boy kissing Kit on the cheek you can see Ellen Sue sitting down behind her, but when they cut back to the dance floor Ellen Sue can still be seen dancing.
When Kit and Dottie are talking in the locker room after the World Series' final game, Kit's hair is pulled back by bobby pins and her bangs are messy. However, a few moments later when Kit is getting into the Racine bus, as she's waving goodbye to Dottie, her hair has fancy barrettes and her bangs are neatly cut.
When Marla is leaving home, her father sees her off from the station. As the train starts to leave, the flag is reflected in the window as Marla looks through toward the rear of the train and her father. In the next shot, the flag is behind her father and would not have reflected off the glass that way.
When Kit becomes unduly upset after the last game of the World Series, she is shown hunched over, weeping, and holding her mitt over her head, wearing her jacket over half her upper body; the camera cuts to Dottie watching her, Kit is shown again in a long shot, same posture, but the jacket is gone.
While Dottie is waiting for Kit to sign a girl's ball after the World Series game, we see a stadium vendor walk into the restroom behind Dottie. In the very next shot, he walks into the restroom again.
There is an approximate 4.3 second gap where the camera cuts away from Jimmy holding an unfolded towel to Alice, before returning to Jimmy where the towel in his hand is now folded. It's not completely implausible that he could have folded the towel in those 4.3 seconds.
When the initial team tryouts are being held in an ivy-walled stadium (obviously Chicago's Wrigley Field) there is a shot of Betty Spaghetti running back to make a catch in the outfield in front of a plywood wall that is clearly from another field.
Lowenstein is in the room with Jimmy when Miss Cuthbert is throwing up because she has been poisoned but later at The Suds Bucket Dottie tells the girls they have to leave because Lowenstein is on the way.
On the last play of the movie, when Kit rounds third, Dottie is shown catching the throw from Doris at third, but when stretches her arms out to apply the tag, she does not have a ball in either her catcher's mitt or her bare hand.
When Mae is teaching Shirley how to read, a multitude of other things are also going on around the bus. One of which is Doris telling Kit and Betty about her boyfriend. At this point, Kit is sitting in front of them with her hand on the back of her seat. You can tell by the way she's holding her hand that the nail polish on it is wet. Mae didn't put nail polish on Kit's nails until the scene where Dottie and Jimmy talk about her husband. And if you look in the background of that scene (where Kit is wearing the exact same outfit), you can see Kit get up and go sit behind Doris and Betty, and you can see Mae teaching Shirley how to read.
The pitchers are clearly seen using an overhand delivery. But the movie takes place during the AAGPBL's first year, 1943, when the game more resembled fast-pitch softball than baseball and an underhand delivery was used. Overhand pitching wasn't accepted as standard in the league until the late-1940s.
The end of the film notes that the players of the AAGPBL were "the first women ever to be inducted into the Baseball Hall of Fame." Actually, they are not inductees. Rather, they were recognized with a permanent exhibit in the National Baseball Hall of Fame and Museum, entitled "Women in Baseball," in 1988. The first woman to actually be inducted into the Baseball Hall of Fame was Effa Manley, the co-owner (with her husband, Abe) of the Newark Eagles. She was inducted in 2006.
When Mae (Madonna) catches the ball in her cap, it's not an out. A player can not use any part of the uniform to trap or catch the ball. Other than the pitching delivery (underhand), size of the diamond (smaller), and size of the ball (larger), the rules are the same in the AAGPBBL as it was in MLB.
When Dottie and Kit first meet Mae and Dorris at try outs, Kit looks around and comments, "Are all these girls going to be in the league?" It is then revealed that out of the 100 girls that were at try outs, only 64 girls would be select to make up four teams of 16 girls. 32 girls received train tickets home. During the actual 1944 AAGBL tryouts in Chicago, scouts sent 280 girls to the try outs, but only 60 girls were selected to form four team of 15. 220 girls were given train tickets home.
In the opening baseball scene, Dottie goes up to Kit and states there is a whole in right field so if an inside pitch she will have to pull it. A right handed batter pushes to right and pulls to left (especially if an inside pitch).
In the final game, a crowd shot shows a solider in his Class "A's" with service cap stand and cheer. The soldier wears the stripes of a corporal on his sleeve, but on his service cap he wears the eagle cap device of a commissioned Army officer, not the round cap piece of an enlisted soldier.
During Marla's tryout in Colorado, Marla's father says "now left handed" and Marla begins to hit left handed. The problem is that the pitchers change and proceeds to pitch left handed. In baseball a switch hitter hits from the opposite side of where the pitcher pitches.
When the bus driver is quitting on the side of the road, Dottie's sweater has a monogram on it. The monogram is wrong, with the H as the third character and a large C in the middle. A monogram would have a large H in the middle since it's her last name.
In the softball scene at the beginning of the film where Dottie gets the game winning hit to score two runners. You can see the ball come off the top of the bat when Dottie swings. In the next short clip you can see the center fielder slowly coming into the infield to make a play on the ball. And I believe you even start to see the ball initially come down just past second base in the infield for a split second. However, the footage immediately changes to a shot of the center fielder running farther in the outfield and the ball landing well past the center fielder.
During Marla's tryout in Colorado, Marla's father says "now left handed" and Marla begins to hit left handed. The problem is that the pitchers change and proceeds to pitch left handed. In baseball a switch hitter hits from the opposite side of where the pitcher pitches. However, this isn't practice, it's a demonstration of Marla's abilities, so Marla can hit whichever side is necessary to show her off. The pitcher was just tired, and gave way to someone else.
In the beginning of the film Dottie's daughter says that she will miss her flight. However, Dottie took a bus to Cooperstown and no plane is ever shown. However, Dottie is coming from cross-country, and there isn't a major airport at Cooperstown. It is entirely feasible that Dottie flew to a nearby airport (Buffalo, Albany, or even NYC) and then bussed from there. Dottie can also be clearly heard saying "a plane, train, and then bus? I'm tired already".
The child actor playing Stillwell looks off camera (presumably towards the director) before falling, after he is hit with the baseball glove thrown at him. But he's stunned so he doesn't necessarily know where he is looking.
The car in which Dottie and her husband drive off (presumably to Oregon) has an "A card" sticker for gas rationing. Would they be able to buy sufficient gas to drive to Yellowstone National Park and back to the Midwest during the course of a 7-game World Series, or had time to make the drive, given the 35 mph wartime speed limit?
The goof items below may give away important plot points.
When the older Dottie is looking at Jimmy Dugan's photo and bio poster at the museum, the line "Born 1906 - Died 1987" is clearly not there in the wide shot, but instantly appears underneath his bio paragraph in the close-up shot; possibly because they didn't to reveal that he died until the close-up shot.
When Dottie initially quits the team, she tells Jimmy that she and her husband are driving back to Oregon. However, gasoline was rationed during the war and prominently displayed on their windshield is an "A" sticker, which entitled the holder to 4 gallons of gas per week. Dottie later says that they drove as far as Yellowstone National Park and turned around. They would never have been able to purchase enough gas to get from Rockford to Yellowstone and back.
Before the World Series, Kit was traded (not sold) to the Racine Belles. That means the Rockford Peaches should have received a player of comparable value in return, but we never see the new player. There's only 16 women per team, so the new player should have been apparent immediately. It's likely the film makers just chose not to introduce a new character this late into the movie to keep things simple.