Plot hole: In Season 1, Episodes 5&6, it's mentioned several times that Zoey is already 19 a few weeks before she starts college. Yet in this episode, Charlie points out to Leo and the President later tells Oliver Babbish that Zoey was 17 when she was filling out her enrollment forms for college, therefore a parent had to sign them. These are enrollment forms, not application forms - it's extremely unlikely that they were filled out over a year before she started school.
Continuity mistake: When Bruno and Bob are poring over exit polls, they mention that Santos seems to be leading in North Dakota, and comment that it is a state that hasn't gone Democratic in forty years. While that is true in the real world, in the fictional West Wing world, it is stated in Season 4 that Bartlet won the Dakotas in his landslide reelection.marathon69
Factual error: When Leo is reminding the Congressional Aides about their bosses' drug scandals, he states that Vicodin is a Schedule II Controlled Substance. At the time the episode was shot, Vicodin was a Schedule III Controlled Substance. Given his experience in this area he'd know better.
Factual error: Sam says the "state-of-the-art" oil tanker he recommends can carry 2.2 million gallons of oil and weighs 308,000 tons. The Exxon Valdez could carry over 60 million gallons (1.48 million barrels) and weighed only 211,500 tons. The writers mistakenly swapped 'gallons' for 'barrels' so that this enormous tanker carries very little oil. It would actually carry 2.2 million "barrels", which equals 92 million gallons.johnrosa
Deliberate mistake: This show is famous / infamous for having many long conversations between characters that are walking the corridors of the West Wing of the White House. In this episode, the chat was long enough that more space was needed to complete the walk, so the actors were instantaneously teleported to a different spot to lengthen the walk. Using http://www.whitehousemuseum.org/special/wwtv.htm as a guide, Pres. Bartlet and Leo leave the Oval Office, pass through the Presidential Secretary's office, turn left, passing between the Roosevelt Room and the Chief of Staff's office. At the end of the Roosevelt room, they turn left through dark wooden doors that are open. Instantly, the actors are at the next junction higher on the map (no wood doors), as if they'd just passed between the Roosevelt room and the Communications Bullpen, and they continue (downward on the map) through the intersection where they original turned (watch for the doors after Leo says "You wouldn't understand"). (00:02:40)johnrosa
Audio problem: As Charlie leaves the Oval Office, he pulls the door behind him. When it stops moving, the audio suggests it has been closed fully ("ka-chunk"), yet it's obvious it has not been closed as we can still see the outer office's curtains at the right of the screen, confirmed further when C.J. steps forward and the camera pans right to show the entire door frame area, and the door open quite a bit. (00:37:30)johnrosa
Plot hole: As Josh arrives at the security gate of the White House, protestors are gathered, chanting and otherwise talking loudly. He enters the gate, makes his way to the north entrance of the West Wing, and as he enters the lobby, the crowd is still heard quite plainly, just as loudly as at the gate, as if they were right outside the door, yet the protestors are much too far away to be heard so loudly, if at all. (00:00:40)johnrosa
Continuity mistake: When Toby is walking back to his office from the press room with his ex-wife, the ex-wife's tag and chain keeps changing through the entire sequence. Sometimes it's over her jacket and the tag's just hanging or it's under the jacket and the tag is sitting just inside her jacket.
Plot hole: The Zoey Bartlett kidnap crisis cliffhanger that stretches across the end of Season 4 and the beginning of Season 5 makes no sense in terms of time. Charlie pulls out a note from his wallet that says they will dig up a bottle of champagne on May 7 - Zoey's graduation night. They do. Later that night she is abducted. She is gone three days. Four days later (in "Jefferson Lives") Abby chews out Leo, saying, "It's only been four days and her bruises have not yet begun to heal." The date should be May 14th. However, "Jefferson Lives" supposedly occurs on the Fourth of July - Zoey says it's the Fourth and they all watch the Capitol Fireworks at the end. Boy, that sure was a short month of June.
Factual error: In the scene where the Secret Service chief is in the car with Bartlet and he suddenly realizes Bartlet's injured, he yells to the driver to get to GW Hospital and the limo does a screeching U-turn on what appears to be the Arlington Memorial Bridge. At the time they were supposed to be heading from Rosslyn, VA, where the event was, back to the White House. But GW is in DC, not that far from the White House, so although the U-turn looks cool, it doesn't make geographical sense. Also, in that one shot of the outside of the car, it appears to be pouring, while back at the scene of the shooting as well as ahead of them at the hospital entrance, it's not.
Revealing mistake: Oliver Babish's office has windows in a location it can not possibly have them. Jed and Leo are in continuous conversation as they leave the 'normal' West Wing set at the end of a hall (See http://www.whitehousemuseum.org/special/wwtv.htm where the words 'Press Briefing Room' are - that's where they turn to their right). They walk a few steps then turn right again and ahead of them is Babish's office, with windows straight ahead. If this had been a single continuous set, Babish's office would be located in the stair area to the left of the press briefing room, and the windows would offer a view of the hallway that runs between the lower corners of Leo and C.J.'s offices (seen at 3:36), not the outside world. (00:03:30)johnrosa
Other mistake: I call this one an "Escher Mistake". As Donna and Josh near the end of their chat about the chair that needs repairs, they pass an office door on their left (Nancy McNally's office) just before going through another doorway. The camera that follows them passes "through" a solid wall and emerges in an office, facing a hall and stairwell as Josh and Donna enter from our left as if this has all been a continuous shot. But the camera-through-the-wall moment is actually a cut so that the actors can be on a totally different part of the set. This would be fine, except the staircase they are about to turn left to and climb only rises up about 3 feet, then the user turns left again and heads to our left - but that sends the user into McNally's office, and does so 3 feet off the floor, yet they are seen entering the press room instead. (00:11:50)johnrosa
Visible crew/equipment: At the end of the episode there is a camera visible in the oval office. After President Bartlet and Toby leave the office an attendant enters to turn off the lamps in the oval office. The scene widens as the lamps are turned off such that the audience can see the entire darkened room. The production equipment, a camera on tripod, and even a crewmember's leg are visible between the penultimate and final lamps being turned off. (00:41:50)