Right before the scene where Lindsay gets hit with the ball, the legend on the screen says it's July. The ball Miguel Tejada of the Orioles hits into the stands, which hits Lindsay, is thrown by Mike Myers of the Red Sox. Mike Myers wasn't picked up by the Red Sox until August 6, 2004.
During the party scene we hear the song "O Babe, What Would You Say" By Norman 'Hurricane' Smith. The saxophone player at the party seems to be playing but it is the sax solo from the original song that we hear.
When Lindsey gets to her seat, at the game in which Ben is selling his tickets, Johnny Damon is clearly in center field, as it is the top of the 9th, and the Red Sox are on defense. However, when she looks through the binoculars, the first base coach is from the Red Sox, and the first baseman is a member of the Yankees, meaning the Yankees were playing defense, and the Red Sox were batting.
When Lindsey is talking to her mom in the kitchen, there is a plate on the counter with only four cookies on it. In the next shot, when her mother picks up the plate to offer some to her, the plate is full.
When Ben and Lindsey are having their BBQ in the park, Ben is holding his cup in his right hand. Change angle on shot, and he is gesturing with his right hand, now empty. Change angle, it's back again.
When Lindsey goes to Ben's apartment after returning from her parent's house, they go into his bedroom where Ben gives her the Red Sox jacket. In first few shots of her wearing it, the American flag is visible on the front of her right shoulder. However, for the rest of the scene, the flag is not visible at all.
While they eat their first meal together, when Ben is taking a message on Lindsey's cell phone ("this is Ben her house boy/sex slave... call your mother") Lindsey's hands change places from under her chin to her lap between camera angle changes.
When Ben drives Lindsay home from the airport, Lindsay is wearing a beige top under her jacket, but as the scene progresses, her top goes from beige to a red and white striped top, and changes back and forth.
When Ben misses the Yankee game to be with Lindsay, Tony calls while they're in bed. The clock on the bedside table says 10:37. Ben turns on the TV to check the coverage and within the same news coverage, the time jumps to 11:27 and back to 10:40.
Lindsay's office is first shown to be in the John Hancock Tower (big blue glass building), but towards the end of the film it's shown to be in the Prudential Tower (which has "GO SOX" lit up in the windows).
The Park scene, according to City of Boston Park rules and regulations, could not legally exist. Ben says in his 'list of things I like about you' Lindsey drinks in the middle of the day, inferring that there is liquor in her cup. According to Section 1 Subsection G 'No person can have in his or her possession intoxicating liquor'. Also Ben is having a BBQ, according to Section 3 Subsection J 'No person can make a fire'.
When Ben attends his first game in 1980, as he and his uncle walk up the ramp and sit down, the score board on the Green Monster changes from the old version (AL scores only) at Ben's first glance, to the newer version (including the NL scores) faintly visible behind batting practice players and back to the old version.
In the scene where it is revealed that the Yankees officially clinch the division, the "F" indicating the final score goes up from inside the hand operated scoreboard while an inning is in progress. At Fenway Park, the out of town scores are changed between innings from the outside and only between innings.
After Lindsay is hit with the foul ball, they watch the replay
on SportsCenter. The announcer says Miguel Tejada (the Baltimore Oriole's Shortstop) hit the foul ball. But on the clip, the batter is white. Tejada, who is from the Dominican Republic, is dark skinned.
With about ten minutes to go in the film, and during the "attempt to buy the season tickets" scene, if the viewer looks at the top of Fenway crowd scenes, we can see a "dummy board" which fills in the top of the shots. Those "people" at the top of the shots, have been painted in to look like fans sitting up top and in the background.
When Lindsey is looking through the binoculars, she appears to look through them backwards, with the smaller "eyepiece" facing outward. She is actually looking through them correctly. The particular binoculars are a compact style that uses a reverse Porro prism design, which allows the objective (outward) lenses to be closer together. When she has them in her hand, you can see rubber eye cups on the end she holds to her face.
When Lindsey is running across the field, it appears that she throws her purse at a security member. Seconds later she runs around Johnny Damon and her purse is back in her hands for the rest of the scene. However, she actually takes Damon's glove and throws that at a security member, not her purse, which correctly stays on her arm during the entire scene.
The goof item below may give away important plot points.
The final scene when Lindsay runs across the field is ripe with errors. First, the broadcast would not have shown her on TV (networks do not show streakers to discourage people from doing it). Next, the security guards would never have let her reach the home plate stands, let alone stand and talk to Ben. Finally, the Green Monster scoreboard clearly depicts the top of the fifth inning against Tampa Bay - not the 9th inning of game 4 of the ALCS, when the scene takes place.
In addition to incorrectly showing Lindsey's dash across the field on TV, she is shown from a handheld camera that must be *on* the field. There would be no such TV camera on the field during a game, only after the game has ended.