Alternative Character Interpretation: Chaucer has been the subject of intense study over a very long period, so as you might expect, there are many. For example:
The Prioress used to be thought of as the target of fairly light mockery, but in part due to the violently anti-Semitic tale she tells, modern critics have found evidence of a more condemnatory intent. This may well, however, be a case of Values Dissonance.
Terry Jones (yes, thatTerry Jones) wrote a book, Chaucer's Knight: The Portrait of a Medieval Mercenary, arguing that far from being an ideal hero, the Knight was actually an amoral mercenary, and intended as a Take That! against someone Chaucer knew.
Some indication of the factitiousness of Jones's theory may be grasped by his reference to The Teutonic Knights' "Crusade" in Prussia as having attracted a great deal of criticism, thus discrediting the Knight, who had fought there. Though the Teutonic Knights' Polish enemies had denounced the Prussian campaign, it is highly unlikely that Chaucer would have endorsed their opinion, even indirectly, since his own patron (and in-law)'s son had "reysed" in Prussia, and was proud of the accomplishment — even after coming to the throne as King Henry IV. (In comparison, Chaucer does poke fun at the Squire's aspirations towards chivalric gallantry, as he refers to his having fought "in Flaundres, in Artoys and Pycardye," referring to a then-recent military campaign that had been an unmitigated disaster.)
From the opposite ideological angle, while "The Franklin's Tale" comes across to a modern audience as a positive argument for equality and respect in marriage, some have argued that Chaucer intended these features to represent a bad marriage. The franklin is compared to Epicurus in terms of being something of a glutton,note As Epicurus was reputed to be, though there's no real evidence of this. and at the time the philosopher was also known as representing evil atheistic sentiments, but he still wins his argument with the Nun's Priest and the Wife of Bath.
The Pardoner. While he is indeed a morally bankrupt charlatan hawking religious snake-oil to the gullible, he makes no pretense that he isn't one, and almost seems to acknowledge that he's probably not virtuous enough to be anything else. Compare this to say, the squire (see above) who pretends to be a war hero but isn't, or the monk, who preaches on and on about virtue and the downfall of famous people while living a very worldly life himself. Alternatively, the pardoner could just be so self-unaware that he does not know he is being a hypocrite.
Did the knight in the Wife of Bath's Tale truly learn his lesson? When he decided to let his wife choose between beautiful but unfaithful and ugly but faithful, did he finally understand the value of giving women a chance of make their own decision or he dislike both options equally and couldn't decide?
Fanfic Fuel: An Older Than Steam example. The unfinished state of both the poem itself and some of the tales (particularly "The Squire's Tale") has led to poets writing their own continuations, starting almost directly after Chaucer's death.
First Installment Wins: Chances are that if people are familiar with any story or character in the Tales, it's the Knight and his Tale, who is the first, or occasionally the Miller, who is the second.
Fridge Brilliance: In The Knight's Tale when Emily prays to Diana to spare her from a bethroal, she says that she loves hunting and being a wife and mother will interfere with that. However this is the only time that particular hobby of hers is ever mentioned or even hinted at. Emily is praying to Diana because she's the goddess of virginity: who better to intervene on her behalf? But Diana is also the goddess of the hunt; what better way to butter her up than to falsely claim to be a huntress who will suffer if the marriage plans go forward?
Glurge: The Prioress's Tale, complete with the unfortunate implications common to glurge in spades. Whether this was intentional is unclear.
The Prioress cannot abide cruelty to animals — nor can she abide a lack of cruelty to Jews. Hmmm...
Even back then, there was probably an implication that she had a major case of Moral Myopia (even if the anti-Semitism would be condoned). Some scholars have noted that it was common when writing of virtuous characters to start with good manners and love of animals and then move into their charity toward the poor. Chaucer makes you expect that he'll start talking about her charity, but he doesn't — it's pretty clear she's nicer to animals than people. Also, historically anti-Jewish predjudice has often had an Even Evil Has Standards aspect in some corners. It is not implausible to imagine Chaucer disliking Jews while satirizing other anti-Semites, simply on the grounds that "they didn't deserve to be treated that badly."
Signature Scene: From "The Miller's Tale", Allison tricking Absalon into kissing her butt is the most well-known scene of the story, owing to its sheer absurdity.
Spiritual Successor: The literary scholar Harold Bloom speculated that Chaucer deeply influenced William Shakespeare, finding a successor to the Wife of Bath in Falstaff and a successor to the Pardoner in Iago. Shakespeare's play Two Noble Kinsmen is a remake of The Knight's Tale; another Shakespeare play, Troilus and Cressida, is a remake of a Chaucer poem of the same title.
Unintentional Period Piece: This work is, in a way, a chronicle of the lives of people in the Middle Ages, who are heading off for pilgrimage to the tomb of St. Thomas Beckett at Canterbury. That tomb was demolished by orders of King Henry VIII during the English Reformation, and only a candle now sits on what used to be the spot of the tomb of the cathedral.
Attitudes about a great many things have changed a great deal since Chaucer's time, and some of the tales (e.g., the Prioress's tale, with its egregious anti-Semitism) have massiveUnfortunate Implications by contemporary standards.
Endless debate rages about whether Chaucer's own point of view would have aligned more with traditional medieval values or with some of his more liberal-minded characters. Cagey SOB that he was, Chaucer intentionally depicts himself an Unreliable Narrator, possibly to provide plausible deniability in case any of his stories attracted unwanted attention.
Out of the Wife of Bath's five husbands, the one she truly loved was the one who physically and verbally abused her and insulted women in general and actually made her half-deaf. And she still loves him. In addition, while her independence and views might evoke some Values Resonance, she maintains that while she likes her lifestyle, she doesn't think all women should do it and insists that remaining a virgin is better. She just doesn't want to be one herself.
The rather comical depiction of rape in "The Reeve's Tale" would be viewed very differently today, as would Alysoun's Questionable Consent in "The Miller's Tale".
Values Resonance: The titular character in "The Wife of Bath's Tale" is very independent and has views on women's sexuality that are very ahead of her time.
(and in-law)'s son had "reysed" in Prussia, and was proud of the accomplishment — even after coming to the throne as King Henry IV
Unfortunate Implications by contemporary standards.