This alchemical interpretation is the only one I can think of that unites the various details in all three Fool cards (adding the Noblet) in one coherent allegory. I think that the PMB Fool card (http://4.bp.blogspot.com/_5e7P4Y3Wo3w/S ... vegni1.jpg, with Giotto's) says the same thing in Christian terms. That one is the Fool who dies at Carnival and is reborn, after seven weeks of putrefaction (the seven feathers in his hair), at Easter.
After re-reading Moakley (The Tarot Cards Painted by Bonifacio Bembo) and some other literature, I have to take back what I said about the PMB Fool card. That one, with the feathers on his head, is the personification of Lent, not the King of Carnival. The Giotto is a representation of him in his foolishness, preaching to the crowds from the sidelines at Carnival, about how they will burn in Hell unless they stop their materialistic excesses. Meanwhile he has a pot-belly himself. Here are both of them.
Moakley (p. 115) thinks that the protrusion indicates pregnancy; well, that is another meaning to this polysemous image, that he bears within himself the Resurrection, but not the primary one; I agree with Andrew Ladis, in "The Legend of Giotto's Wit and the Arena Chapel" in The Cambridge Companion to Giotto (at http://books.google.com/books?id=5CByQQ ... it&f=false, go to "contents" and then p. 225). He says.
Stultitia (Fig. 46) is a dumpy oaf who perches on a low rock and raises a heavy club to the heavens as he lets out a tongue-wrench screech. Spherical objects, probably stones, hang from an engirdling belt as thick as his wrist and keep this dodo on the ground. Like an exotic, avian prince, he sports a crown of bells and feathers and wears rags that trail behind him in a mock-elegant train. In the trecento, bloated, barefooted, would-be birds like this were a source of laughter.
Ladis has three long footnotes justifying this interpretation further (18, 19, and 20, on p. 289-290 of The Cambridge Companion to Giotto), but I think you get the general idea. He does not relate the image to Carnival; that is Moakley's idea (p. 114), and it is a good one.
However the PMB Fool has no paunch; in fact he looks emaciated. He is more an object of pathos than of pretentiousness. It is a different representation of Lent. He is someone who through foolishness, either natural mental retardation or acquired in the course of an arrogant and ignorant life, is involuntarily in the state that other people affect voluntarily during Lent. He is the Fool as penitent. And if he is truly penitent, and follows the lessons of the 21 numbered trumps of the tarot, perhaps he will be reborn at Easter.
The personification of Lent, on some accounts (http://www.fisheaters.com/customslent2.html), was burned in effigy on the evening of Easter Saturday, when the Lenten fast is broken. Other accounts have that figure as Death or Judas. During Lent, Moakley says, Lent's feathers "are pulled off one by one as the weeks of Lent pass." Her reference is Frazer's unabridged Golden Bough III, "The Dying God," pp. 244-245. These pages can be found, among other places, at http://www.archive.org/stream/cu3192402 ... 9_djvu.txt.
Yet I still think that the PMB Fool is related to the d'Este Fool and "Mantegna" Saturn. They--as well as the more obvious Jester figures in other decks--are the Carnival King, who is also foolish (Carnival derives from the Roman Saturnalia). The Carnival King meets his end at the end of Carnival, when he is overcome by Lent, Moakley tells us (p. 63), as in Breughel's painting "The Battle of Carnival & Lent" (http://en.wikipedia.org/wiki/File:Pieter_Bruegel_d._%C3%84._066.jpg; Lent here is an old woman, as she often is in the descriptions of personified Lent). It seems to me that the Noblet, since he has both the Jester's hat and the rags of the PMB, combines both figures, Lent and Carnival, in one image. He is the Carnival King not yet penitent, but on the way.
Moakley adds that the Bagatto/Bagatino/Magician is often in the role of the Carnival King, the one whom Lent defeats. Thus he sometimes has the costume of the clown or jester. But that is another thread.
Moakley gives a list of other representations of the Fool as Lent or the Carnival King, some of which I have not seen, or noticed if I did see them. Most are in Hind's Early Italian Engravings. He is also in representations of the month of March, the month of Lent and penitence.
Two examples that occur to me (not mentioned by Moakley) are the "Wayfarer" paintings by Bosch. (There is also his "Stone Operation," already discussed on this thread; that is a different sort.) In the Rotterdam painting above, 1488 or later http://en.wikipedia.org/wiki/File:Wayfarerbosch.jpg), a wayfarer, somewhat the worse for wear, is shown hobbling away from an inn, where he no doubt partook of various nefarious activities, some of which are pictured. Art historian Laurinda Dixon comments:
The wayfarer's bad foot suggests that he has paid an excruciating price for overindulgence in the vices harboured by the ramshackle tavern. The closed gate towards which he heads suggests that perhaps the door to salvation will not open easily for him. (Bosch pp. 94f.)
That bad foot is also a characteristic of Saturn, for example in the Sforza's 1460s De Sphaera (http://cache2.asset-cache.net/xc/898678 ... 6CF65BF77B).
[Added next day:] Also, lameness is a symbol of his castration. In the ancient world, the foot or leg was a euphemism for the phallus, as the third lower member; for example, the name "Oedipus" means "swollen foot" and is thus not only descriptive of the forgotten maiming he received from his father but also his over-abundant sexual interest in his forgotten mother.
In contrast, the Prado Wayfarer (below middle, 1510 or later) is in better shape. His foot seems normal, and the rickety gate leading over a stream suggests a path toward heaven. Dixon says:
Whereas the path in the Rotterdam is blocked by a closed gate, that in the Prado panel leads without impediment across a small footbridge. In general, the Prado Wayfarer, though threatened, seems untouched by the elements of folly, danger and death that surround him on all sides. (p. 99).
Later in the chapter, Dixon shows us a German woodcut of c. 1488, the Mirror of Understanding, of which I show the relevant detail below.
In common with the Prado Wayfarer, the Christian pilgrim in this image advances across a footbridge that leads from this life to the next. (p. 103)
These wayfarers seem much in the spirit of Moakley's characterization of the PMB Fool as Lent coming out of Carnival. Other elements in the paintings suggest the "Marseille" fool: the ragged clothes and threatening dog, for sure. The stream, too, appears in at least one version, i.e. the "Chosson" of 1672 (2nd above, left). In the Noblet 2nd above, right), that stream appears instead beneath the Bateleur's table.
[Added next day]: In the upshot, the PMB Fool, as much as the "Marseille," marks the transition from the materiality of Carnival to the spirituality of Easter, through penitence, meditation, and abstention. He is thus, like them, another symbol of what alchemy called the fixation of the volatile (his materialistic excesses as Carnival King) and the volatization of the fixed (a shift toward the spiritual)--also the transformation of Saturn into Christ--and not simply the putrefaction, in Lent, following the death of the Carnival King and preceding the albedo as Resurrection.