In the previous episode, when Picard, Riker, Crusher, La Forge and Troi go through the temporal distortion that sends them back to 1893 they are only carrying tricorders. None of them is carrying phasers, at least not the larger type-II phasers. It's possible they could be armed with the smaller concealed type-I phaser. At this point, they know that these aliens are a threat, so Starfleet regulations dictate that they would need to be armed, and, in situations where combat is likely, they always use the more powerful type-II phaser. However, both Riker and La Forge are both shown using type-IIs. Data was carrying a type-II, but he had to dismantle it in order to build his improvised temporal scanner.
The Devidians are shown teleporting through time unaided on several occasions, yet one of them uses the doorway in time generated by Data's detonation to flee in desperation after failing to reacquire the snake-head staff. He should be able to simply teleport away again.
Picard is changing lamps and is questioned by a doctor. The doctor responds, "There hasn't been an earthquake here in thirty years." This is set in August 1893, and according to the Virtual Museum of the City of San Francisco, on June 6, 1893, there was a "strong earthquake...and many men in downtown offices rushed to the streets." There were in fact dozens of earthquakes in the 30 years prior to 1893, including sizable earthquakes in 1892, 1890, 1889, 1888, 1885, 1883 (the strongest since 1868), and on with noticeable earthquakes nearly every year.
Just before the torpedoes impact Devidian II, Picard reappears in the caverns. Data informs Riker that they have detected human life signs, plural. As Picard is the only human there, they would have only detected one human life sign. Data, an android given to extreme precision, would not make such an error.
However 'human life signs' does not necessarily mean more than individual. Multiple indicators ('signs') used as to determine the presence of human or other life.
When the bellhop Jack London is speaking to Samuel Clemens about having any dreams or dreams, he mentioned that he'd like to visit Alaska. Alaska didn't become a state of the Union until 1959, this episode was based in 1889. There's no way he would know about Alaska for another 130 years.
However, it was a well-known territory that many people had visited or at least knew about. The Russians named it 'Alyáska' (from an Aleut phrase) in the 17th or 18th century.
When the crew make their getaway from the hospital, it is obviously a stuntman in makeup and not Brent Spiner driving the carriage.
Each time any actor holding the snake head cane device moves it around a bit too quickly, it wobbles, revealing it to be made of rubber.
When Geordi is working to reactivate Data with his 500 year old head, the supposedly immobile Data can be seen wobbling and shifting numerous times.
After he loses his head, Data's body becomes rigid, yet his extended arm (holding the snake-head cane aloft) can be seen shaking and wobbling as if fatigued.
Picard uses Data's head to send a message to the Enterprise in the 24th century. It would be much easier to simply tell Guinan, whom he knows will also be on the ship in the 24th century. The information wouldn't be anything that Guinan or anyone else could use to change the course of history and she could be trusted by the captain as much as Data could. There's also no guarantee that Geordi would be able to reattach Data's head and get or correctly interpret Picard's message, making Guinan the better choice.
When the real police officer arrives at the hospital after the ruckus with the aliens, he says, "Someone reported gunfire." But there had been no gun fire. The Enterprise people fired their phasers, but that would not have been interpreted as gunfire.
Dr Crusher tells Commander Riker that the field generated by the "cane" can only be balanced for one person. Riker decides this means if he travels back to rescue Captain Picard, only one of them could come back. But a few hours before, an entire away team returned successfully, even those who did not have physical contact with device. Even if only one person could enter the field at a time, Riker could have returned to San Francisco, found Picard, activated the field to send Picard back, and allowed the field to dissipate before re-activating it to return himself.
Data is able to acquire money, a room in a hotel, fine clothes, and numerous supplies for building his experimental devices within hours of arriving in the past.
The rest of the bridge crew, despite being in the past for some time, is unable to acquire enough money to pay their landlady. Surely the 5 of them put together could come up with some sort of method for earning money. They are able to procure multiple changes of clothes, including police and nurse uniforms, and script books, but not actual cash for paying rent?
Even when they meet up with Data and are confronted by the landlady, at no point does anyone suggest that Data pay their rent out of his considerable monetary resources.
The rest of the bridge crew, despite being in the past for some time, is unable to acquire enough money to pay their landlady. Surely the 5 of them put together could come up with some sort of method for earning money. They are able to procure multiple changes of clothes, including police and nurse uniforms, and script books, but not actual cash for paying rent?
Even when they meet up with Data and are confronted by the landlady, at no point does anyone suggest that Data pay their rent out of his considerable monetary resources.
Data returns to the 24th century Enterprise with a message encoded in his static memory by Captain Picard in the 19th century. The message is very critical, yet Data stops along the way to change from the 19th century clothing to his Starfleet uniform.
Worf tells Riker that if they, themselves, had been in the cave with Data's head, they would have turned to dust over the lapse of 500 years. This is not so. Even in a humid environment the skeletal remains would be found, Items such as their communicators and other equipment would be in decent shape.
Samuel Clemens pronounces Halley's Comet as "Hayley's Comet", a common mistake.
Samuel Clemens only played the part of Mark Twain when on stage, or in a public performance.. If he was caught in an elevator, or room, he would have been himself. NOT, Mark Twain.