Dickens uses situational irony to critique the practice of imprisoning debtors, something that happened to his own father. For example, in Chapter 11, the narrator writes of the Micawbers:
[...] they lived more comfortably in the prison than they had lived for a long while out of it.
The Micawbers are both comedic and tragic figures. They seem incompetent at managing their own affairs, to the point that they almost read as a cheap shot at Dickens's own father for mismanaging his money. Still, they are essentially good people who get caught in a system that makes it extraordinarily difficult for them to fix their own errors. Debtors, or people who owed money they could not or would not pay back, were regularly thrown in debtors’ prison in England until 1869. Debtors made up a huge percentage of inmates—over half, by some counts. Imprisoning debtors created a vicious cycle because it was next to impossible to make money to pay off debts while imprisoned. As is still the case today in many places, poverty and incarceration created the conditions for further poverty and incarceration.
Dickens himself faced the far-reaching social consequences of this system as a child. It was the life of Dickens's entire family, not only his father's life, that was disrupted by debtors' prison. The novel uses the Micawbers to explore the way debtors' prison affected whole families. After Mr. Micawber has been in debtors’ prison for a while, Mrs. Micawber moves the whole family there for cheapness and convenience. It is absurdly ironic that the quality of life in prison is better than the quality of life the Micawbers have enjoyed out of prison. Prison, an institution that is supposed to take people out of daily public life, might as well be the new site of public life if people are picking up to move there for a better life.
The irony is at once comic and tragic. Readers are left either in a state of deep sympathy for the Micawbers or shaking their heads at a system that is completely laughable. Dickens thus uses situational irony to agitate readers against a social system that he has a personal stake in challenging.
In Chapter 39, Uriah upsets Mr. Wickfield and claims that he is entitled to marry Agnes due to his upward mobility. In the morning he claims to have smoothed things over with Mr. Wickfield while also using a metaphor to suggest that he has already made sexual advances toward Agnes:
I obliged myself to say that I was glad he had made his apology.
‘Oh, to be sure!’ said Uriah. ‘When a person’s umble, you know, what’s an apology? So easy! I say! I suppose,’ with a jerk, ‘you have sometimes plucked a pear before it was ripe, Master Copperfield?’
‘I suppose I have,’ I replied.
‘I did that last night,’ said Uriah; ‘but it’ll ripen yet! It only wants attending to. I can wait!’
Uriah smacks his lips while David rides away in the coach. David might be taking Uriah literally, agreeing that he too has picked an actual pear before it was ripe. More likely, he means that he has counted on an opportunity before it was ensured.
As Uriah goes on, his words and demeanor make it clear that his meaning is more sinister. Agnes is the pear. He could mean that he "plucked" her by swearing that he was entitled to marry her, but he could also mean that he approached her sexually after everyone went to sleep. Agnes is not "ripe" yet because she is not married. If Uriah has indeed approached her sexually, it could mean that she will never be "ripe" for marriage to anyone else, according to restrictive Victorian social mores. As the reader has already seen with Emily, premarital sex can be damning for a Victorian woman and her family. Just as the Peggottys are left at the mercy of Steerforth's decision to marry Emily or toss her aside, Agnes and Mr. Wickfield may now be forced to beg for Uriah to marry Agnes.
Whether or not Uriah is using the metaphor in this crass sense, his "'umble apology" to Mr. Wickfield is laden with situational irony. According to manners, Uriah owed Mr. Wickfield an apology for upsetting him by claiming an inherent right to marry Agnes. In this sense, he has behaved honorably. But by behaving honorably toward Mr. Wickfield, Uriah has laid further groundwork for marrying Agnes after all. Rather than being shooed away, Uriah has secured for himself once more the chance to "wait" and "attend to" Agnes. This irony highlights one of the problems with the extreme importance placed on manners in Victorian society. The well-off Mr. Wickfield, good at recognizing politeness but not necessarily sincerity, is convinced by Uriah's performance of good manners and is thus more easily manipulated by him than if he did not care about manners.