In addition to stock footage of subway trains that was reversed, as noted elsewhere on this page, Lucy and Ethel's subway journey is full of continuity problems. The interior shots with the actors were shot on the Desilu stage, in a mock-up of a subway car with signs on the sides indicating "Lexington Avenue Local", "Flatbush Avenue" and "Woodlawn". The IRT Lexington Avenue Local (today the 6 train) runs between the Bronx and lower Manhattan, not into Brooklyn (where Lucy ends up). It is the express (today the 4 train) that runs from Woodlawn (Bronx) to Flatbush Avenue (Brooklyn). The Lexington Avenue Local would have been the closest line to the Ricardo/Mertz apartment building on East 68th Street (though their address of 623 would have been a block or so into the East River, as the addresses only go into the 500s!). That line does pass through Bleecker Street and Spring Street, in that order, as shown in the episode. The first train seen as an establishing shot for the subway car scenes is marked "AA", which was once a local version of the express "A" train, and is no longer in use today. The "A" route does go to Brooklyn, but it runs on Manhattan's West side, not the East side where Lucy and Ethel were traveling, and does not go through the Bleecker or Spring Street stations. As Lucy leaves Spring Street, the first train shown is marked "7 Times Square" (with a reversed image). This isn't even a North-South train, but rather a cross-town route that ends in Flushing, Queens. This cuts to a second shot, this time of the Westside "AA" train again, marked 168th Street, which would make it a Northbound train. Finally, arriving into Flatbush Avenue station, we see a train marked "New Lots Ave". The only train going to that station is the 3, which travels through Flatbush (Brooklyn), but does not go to Flatbush Avenue Station.
Lucy covers her head with a newspaper - The Daily Chronicle. This is a fictional Hollywood-created newspaper. Coincidentally, The Daily Chronicle turned up again in 1969 during an episode of "Here's Lucy" set in Los Angeles.
The pillar which supports the subway ceiling can be seen to be a prop when it moves as Lucy bumps into it.
The shot of the subway train after leaving Spring Street has been reversed (the #7 on the train is clearly backwards).
Ethel still claims that she has been married to Fred for 25 years. This has been proven inaccurate on many occasions. Ethel may be exaggerating for comic effect.