I've been thinking about feudalism lately and it's similarities to our current society pertaining to status and wealth, and I was curious are there any accounts of individuals of the lower classes securing higher positions in extravagant or clever ways? Clearly the feudalistic system was setup in such away too limit this from happening, but even so, was there anything at all say similar to the fictional character Petyr Baelish from the A Song of Ice and Fire series; perhaps not as a s sinister or clever.
I think the social structure is far more fluid than you give it credit for certainly before c.1300. If you are thinking that the 'feudalistic system' in terms of a rigid pyramid structure then this is certainly not the case for inhibiting social mobility. Other, more pragmatic, factors tended to influence social mobility than abstract notions of hierarchy until into the very later parts of the Middle Ages.
At any rate, specifying a period is rather essential for any kind of detailed answer. The social and economic milieu of the eleventh- or twelfth-centuries versus the fourteenth- or fifteenth-centuries are very different. At a certain point in English history it is rather anachronistic to even discuss these things in terms of 'class', I would argue before c.1200, although after the 1350s I believe that there has been a real social stratification (exemplified by the birth of a 'gentry' group).
Baelish reaches his position chiefly through meritocracy and patronage. Like almost any period in history one's social connections and ability to exceed expectations could enable almost anyone to breach most 'glass ceilings'. William Marshal rose being the fourth son of an English baron to Regent (or Guardian) of England upon his death. The chief reason for his meteoric rise was his martial prowess which earned him first the attention of Eleanor of Aquitaine, then Henry II (who put him in charge of the martial training of his heir Henry 'the Young King'). The Marshal made a fortune through ransoms at tournaments fighting alongside the Young King. He had acquired extensive lands throughout England, the Marches, Ireland, and even retained his French territories after the French reconquest (he was the only landholder permitted to do homage to both John and Philip Augustus - which rather throws a spanner in the spokes of a 'feudalistic' setup). See Crouch's study or the Anglo-Norman Text Society's modern translation of his biography (written shortly after his death in the 1220s) for more detailed overviews.
At the other end of the scale (in almost every sense: chronological, social, gender) is Joan of Arc, who rose from 'low' (if not quite peasant) social status to being an influential and ennobled member of Charles VII's court in the 1430s. Not that she had much time to enjoy it as she was burned at the stake by the English in 1431. Her family retained the titles and some of the wealth, it seems, but it is another example, if extraordinary, of how patronage and what amounts to merit (ie. she was manifestly helping the French cause against the English) can completely destroy any notion of rigid social structure. Here is a collection of my posts on Joan on this sub, with bibliographies found in and among them.
I would recommend reading more widely around the subject, if this is what interests you:
Peter Coss, The Origins of the English Gentry, (Cambridge, 2003) | The Foundations of Gentry Life: The Multons of Frampton and their World, 1270-1380, (Oxford, 2010).
David Crouch, William Marshal: Court, Career and Chivalry in the Angevin Empire 1147-1219, (Harlow, 1990) | The Image of Aristocracy in Britain, 1000-1300 (Cambridge, 1992) | The Birth of Nobility: Constructing Aristocracy in England and France, 900-1300 (Harlow, 2005) | The English Aristocracy, 1070-1272: A Social Transformation, (London, 2011).
Rodney Hilton, Bond Men Made Free: Medieval Peasant Movements and the English Rising of 1381, (2nd Ed., London, 2003).
(eds) Holden, Crouch, and Gregory, The History of William Marshal, 3 vol., (London, 2002-2006).
(eds) Rosemary Horrox and Mark Ormrod, A Social History of England, 1200-1500, (Cambridge, 2006). An excellent set of essays, see especially Philippa C. Maddern, 'Social Mobility', pp.113-133.
Maurice Keen, The Origins of the English Gentleman: Heraldry, Chivalry and Gentility in Medieval England, c.1300-c.1500, (Stroud, 2002).
Phillipp Schofield, Peasant and Community in Medieval England, 1200-1500, London, 2002.
the lower classes securing higher positions in extravagant or clever ways?
Not so much for the peasantry, but a common means of advancement (social and economic, and often political) was by ascending through the ranks of London's guilds, or livery companies. This was not an uncommon course of action for sons of estate owners who were not the heirs in accordance with primogeniture, in turn causing many of them to move to London. By gaining apprenticeships, and mastering certain crafts, such individuals had the opportunity to join the guild as freemen (if not via patrimony or 'redemption'/paying a fee) and climb the ranks of the company and, with it, attain freedom of the city and begin to exercise political power either by voting or by serving as councilmen or aldermen, possibly attaining the rank of Lord Mayor. (See the story of Dick Whittington for one such example.) So, one such means of advancement was though stepping outside of the feudal structure altogether in emergent urban centers, at least in England.