The Comedy of Errors is one of Shakespeare’s early plays, and a farce involving two pairs of twins and mistaken identity. It was written around 1594, so Rory’s statement that it was written in 1590 is just an estimate – the exact date isn’t known. It was published in 1623 though, as that was the first collection made of Shakespeare’s plays.
Richard III is one of Shakespeare’s historical plays. It was written around 1592, so Rory’s guess of 1591 is within the acceptable time-frame and not actually wrong. In real life, it would be very unusual for students to be tested on their knowledge of the dates of Shakespeare’s plays, as they are usually not known for sure. As we never see the actual test, Rory could be studying all the wrong things anyway.
Shakespeare’s Sonnets are a 1609 collection of love sonnets, most of which are addressed to either a Dark Lady or a Fair Youth. It is not known whether these figures are fictional or based on real people. It is not even known for certain whether the sonnets were written by William Shakespeare.
During the study session, Lorelai makes a buzzer noise when Rory gets a question wrong, as if she is on a game show.