The zookeeper is an alcoholic!

Paul Simon later created a children’s book based on this song. He “sanitized” this line by making Rum the name of an animal.

Joe DiMaggio, often nicknamed “Joltin' Joe” was an American Major League Baseball center fielder who played for for the New York Yankees.

Perhaps the most talked about line in the entire song, Simon has often been asked about the inclusion of Joe DiMaggio in the lyrics.

Garfunkel stressed that it happened Joe DiMaggio fit the bars and the beat better.

After DiMaggio’s death, Simon said that DiMaggio represented the traditional American values and the lines were a tribute to his unpretentious heroic stature in America, especially in a time when the popular culture distorts our perceptions of athletes/heros (Lance Armstrong, Barry Bonds, Alex Rodriguez, etc.)

In these days of Presidential transgressions and apologies and prime-time interviews about private sexual matters, we grieve for Joe DiMaggio and mourn the loss of his grace and dignity, his fierce sense of privacy, his fidelity to the memory of his wife and the power of his silence.
- The Silent Superstar, The NYT, by Paul Simon

DiMaggio is also mentioned in the 1989 Billy Joel hit, “We Didn’t Start The Fire”.

Mrs. Robinson has taken on some cultural clout after the film The Graduate came out starring Dustin Hoffman (in his first important role). A recent college graduate sleeps with his parents' friend, whose daughter he later dates (Mrs. Robinson).

The New Jersey Turnpike (shortened to NJTP and colloquially known to New Jerseyans as “the Turnpike”[5]) is a toll road in New Jersey, maintained by the New Jersey Turnpike Authority. Simon counts the cars (much like sheep) to pass the time and potentially ease himself into a deep sleep.

The New Jersey turnpike also has a reputation in American popular culture as one of the most depressing highways in the country as it passes through many industrial areas. Perhaps the scenes from the New Jersey Turnpike and the values–of materialism, urban sprawl, and unfettered capitalism with no regard for the environment–is what is making Simon feel “empty” and “aching.” So there is a note of depression.

Simon attempts to voice his existential concerns — his search for a dream — to Kathy, but we get a sense of restraint because he only tells her when he knows she’s asleep. He wants to be consoled but is scared to share his true emotions with a conscious partner.