For the first time since The Chinese Restaurant, not a single scene of a Seinfeld episode takes place in one of the usual locations (Jerry's apartment, the café, Elaine's office, the comedy club, yada yada yada). In fact, there are no buildings involved at all: the gang's misadventures are all linked to a fateful subway ride.
Each of the protagonists has to go someplace important, but as is often the case, the journey is more interesting and fun than the destination. Therefore we get Jerry meeting an overweight exhibitionist, Kramer hearing tips about a horse race, George skipping a job interview because he meets a woman and, most hilarious of the lot, Elaine missing a lesbian wedding due to a series of delays.
The key to the episode's success is, typically enough, the dialogue, like when Jerry talks to his fellow passenger ("You have something against a naked body?" "I have something against yours!") or George makes a brilliant statement about how he identifies certain women: "I can always feel when lesbians are looking at me. They see me and think "That's why I'm not a heterosexual!"". This time, however, it's Lulia Louis-Dreyfus who steals the show with an outrageous combination of physicality (her exasperated facial expressions) and voice-over, the latter predating Arrested Development by eleven years for its use of bleeped cursing. That scene most certainly qualified as a shocker back in 1991, and it still stands out as a textbook moment of unsurpassed small-screen comedy.