Frank identifies the TV Guide that Elaine took as Volume 41, Number 31. The magazine used on the show had Al Roker on the cover. The actual TV Guide had Patrick Stewart on the cover.
Elaine (Julia Louis-Dreyfus) & Kramer (Michael Richards) are on the #6 train on their way back from Queens to Manhattan, but the #6 only goes between the Bronx and Manhattan.
Kramer (Michael Richards) first has the idea for a coffee table book about coffee tables in this episode. In episode 5.21, The Opposite (1994), however, Kramer tells Regis Philbin & Kathie Lee Gifford the idea originated when he was skiing.
When Jerry brings the cigar store Indian to Elaine, a crew member is visible 7 different times to the right of the table where Elaine's friend are sitting, as the set ends behind the redhead. This may only be in the widescreen version now available on Netflix.
The taxi Kramer is riding when he shows Jerry the wooden Indian has a California license plate.
Elaine and Kramer are shown riding on the #6 subway train and
stopping at Queensboro Plaza. Later Elaine is shown stopping at the same station on the #4. Neither line goes to Queensboro Plaza. Also characters are shown in front and rear-facing seats. Seats on the 4 and 6 trains run along both sides of the car. The Queensboro Plaza stop is also not an underground platform; the trains that run there ride on elevated tracks.
The address on Frank's TV Guide doesn't exist. There is a 1344 Queens Boulevard in Woodside, and another one in Long Island City, but not in Flushing.
George (Jason Alexander) makes the statement that his parents don't read books, yet in episode 5.7, The Non-Fat Yogurt (1993), we see Frank (Jerry Stiller) reading one.
George (Jason Alexander) confesses to having sex in his parent's bed. It's revealed in episode 8.12, The Money (1997), that his parents sleep in separate beds.
How does Ricky know Elaine's name? The name on the TV Guide reads F. Costanza.