Nellie was raped by the clown rapist.
This is not explored in the actual episode, but is a major reason why Nellie made her final break from her mother and her penchant for gossip. When Nellie warns Laura that vicious gossip is being spread through the town about Sylvia, she then suspects that Nellie may have been attacked. Laura won't believe it at first but then as Nellie presses on, she reveals her own
Dark Secret: She, too, was attacked (a few years earlier) by a man wearing a clown mask and a dark body suit. Laura, realizing Nellie may be on to something, goes with Nellie to talk to Sylvia and convince her to tell what happened and that she must ... and right in front of Mrs. Olesen, too. Mrs. Oleson tries to poo-poo the notion but Nels finally gets her to understand that this is no way to disparage Albert (and that she had better stop right now) ... that the rapist was quite a bit bigger than the teenaged Albert. In the end, Charles helps set a trap and the rapist – indeed, revealed as Irv Hartwig, the blacksmith – is taken alive and forced to stand trial. Nellie and Sylvia, meanwhile, begin to support one another through their ordeal and learn the attack was not their faults.
Nancy was raped repeatedly at the orphanages.
A dark reality of the era Nancy would have grown up in ... the 1880s, when orphans were moved from one place to another, often without reason but sometimes because of behavior issues (such as hers). May have been part of her personality.
Mr. Edwards, specifically the book version, was a closeted homosexual.
It's why he's consistently referred to as a bachelor, despite lifelong singlehood being relatively uncommon then, as men were considered "unmanly" if they hadn't fathered children; while he mentions a wife and five kids in
The Long Winter, we never see him with anyone, and Edwards ends that anecdote with "Got no wife and no children anyhow," leaving before Ma and Pa have a chance to comment. It even sounds as if the tax-man he encountered didn't actually
see the wife or children, which could mean that Mr. Edwards had fabricated a family unit to make himself appear "normal." Mr. Edwards' constant movement is out of fear that a growing number of settlers could mean a growing number of neighbors prying into his business, or that he could "slip up" around others and rumors of his homosexuality would spread.
This is also why he goes out of his way for the Ingalls: Mr. Edwards isn't a true loner, but feels compelled to isolate himself to preserve his secret, which precludes his marrying or otherwise having a family of his own. He's likely cut off from any relatives as well, voluntarily or otherwise, so the Ingalls welcoming him into their home is enough for Mr. Edwards to go to great lengths for them, from nearly drowning or freezing to bring the children Christmas presents to giving them a large sum of money without even waiting to be thanked.
Mr. Edwards was a defector from the Confederate Army
Historians have theorized that as a "wildcat from Tennessee," Mr. Edwards would have been in the right location and of the right age to have been conscripted for the Confederate Army (Laura even vividly recalls his "rebel yell," which was a trademark of the Confederates). Many soldiers who saw the horrors of the war chose to defect, and fear of repercussion or social shame meant that a number of these men sought to build a new life rather than return home. Similarly, anyone associated with the rebellious South would not have been welcome up North, leaving the West as a tempting option to these landless men. This might explain why Edwards never seemed to settle down and was constantly moving westward. As Mr. Edwards' true identity has never been confirmed (and since he's suspected to be a composite character), there's no way to confirm his backstory. Another fan theory is that the adult Laura, wishing not to tarnish Mr. Edwards' kindness by mentioning his ignoble past, was deliberately vague about his identity.
note Related but equally unfounded is that perhaps Mr. Edwards might have fled westward after committing murder in his native Tennessee and that Laura concealed his identity for the same reason. Jenny Wilder is the baby Millie is revealed to be waiting in "The Nephews".
"The Nephews" introduces us to Royal, his wife Millie who's revealed to be pregnant and his two mischievous sons, but in "Times Are Changing Part 2", Royal is a widower, older and has a daughter instead. That's because "Times" is set over a decade after the events of "Nephews", when his sons are already grown up and living far away, his wife has passed away between these twelve years or so and Royal grew older and sick.
Some episodes take place in alternate continuities.
Several episodes contradict each other in major elements, such as "The Nephews" introducing Royal's family consisting of a pregnant wife and two bratty sons, but then he returns a widower, terminally ill and with only a daughter. Or when the Olesons purchase Lars Hanson's old house, even though his house was turned into the blind school and subsequently burned down in "May We Make Them Proud". Finally, the TV movies, which are said to be set in dates several years into the future ("Bless All the Dear Children" in 1896, "The Last Farewell" in 1901), further implying that there are different alternate timelines for the show.
