My research revolves around fairy tales and I had this question arise in my head after reading a tale from Giambattista Basile's 1634 Il Pentamerone. The tale that made me wonder about this is called 'Cagliuso' or 'Pippo', but more commonly known from Charles Perrault's variant, 'Puss in Boots'. If you don't know the tale, basically a cat is left to an impoverished boy as his only inheritance, the cat does a series of clever maneuvers that make the boy seem like a Lord, and he ends up marrying well and rising exponentially in status.
Obviously I'm not taking the fairy tale as an account of a true story (talking cats and all), but I wondered about how achievable a determined social climber's journey would have been. Surely, the manner of speech and modes of behaviour/civility (such as how to behave at the table) would have given them away, even if they were able to obtain clothes that reflected a higher status. That said, I'd be really interested to know if there were any recorded accounts of people moving from the bottom up. I'm sure there's some really obvious famous example I'm not remembering, but please enlighten me!
Perkin Warbeck as Richard of York: Not only did young Perkin Warbeck masquerade as a prince, he nearly succeeded in overthrowing King Henry VII of England. In 1491, Warbeck appeared in Ireland claiming he was Richard of York, the youngest son of the former King Edward IV. The real Richard was most likely murdered in the Tower of London as a boy, but at the time there was still much speculation about his fate. Capitalizing on this mystery, Warbeck presented himself as the missing prince, and eventually won support among Henry VII’s political enemies, who included such powerful figures as James IV of Scotland and Maximilian I of Austria.
Warbeck landed in Cornwall in 1497, and he soon galvanized his supporters into a rebel army of several thousand men. But when faced with the possibility of a battle with the king’s forces, the pretender lost his nerve and fled to the coast. He was eventually captured, and later admitted he was an impostor before being executed by hanging in 1499. Warbeck is widely regarded as a famous fraud, but some historians have noted that Henry VII could have fabricated the pretender’s backstory in an attempt to discredit him. With this in mind, there remains at least a small possibility that Warbeck may have actually been Richard of York.
http://www.history.com/news/history-lists/7-people-who-pretended-to-be-royals
Sorry if this isn't up to the usual standards of this subreddit, it's my first attempt to answer a question and my only source is "The Hollow Crown" by Dan Jones.
The book focuses on the War of the Roses, but the final chapters also cover the years were Henry VII reigned. In particular it covers two pretenders who made claims to his throne. One was Perkin Warbeck as described by /u/rsplatpc.
The other was known as Lambert Simnel, although it's unknown if this was his true name. He appeared before Warbeck, in 1487, and also appeared in Ireland. Dublin to be precise.
Described as a "comely youth", with "courtly manners" locals Lords feasted him and coins were minted with his likeness. However he claimed to be Edward, Earl of Warwick. There were two obstacles to that claim, the first was that after rebelling against Edward IV his father was executed and stripped of his claims. If this hadn't happened he might have had a strong claim to the throne.
However the bigger obstacle was that since his fathers execution he had been a prisoner, when Lambert Simnel was being raised as King of England, Edward Earl of Warwick was being held in the Tower of London.
Despite this the pretender was able to gather a large force (roughly 5,500 men) and land in the northwest of England with it. Henry VII defeated this army in battle, which turned out to be the last time Henry or a member of his dynasty had to defend his title through battle. Although most the leaders of the rebels were killed he spared Lamber Simnel.