People love the way Mr. Wickham lies. In fact, when he comes into Meryton as part of the zombie-killing militia, he immediately starts spreading his tall tales to Elizabeth:
One day, during a daybreak spar, the young Wickham landed a severe kick, which sent Darcy to the ground. The elder Darcy implored Wickham to "finish" his son with a blow to the throat. When the boy protested, the elder Darcy—rather than punishing him for insolence, praised his generosity of spirit. The young Darcy, embarrassed more by his father's preference than his own defeat, attacked Wickham when his back was turned—sweeping his legs with a quarterstaff, and shattering the bones of both. It was nearly a year before he walked without the aid of a cane. (16.29)
You've gotta hand it to Mr. Wickham: all his lies have a little hint of truth to them. He does know the Darcy family, and he was injured by Mr. Darcy as a boy, but the circumstances are quite a bit different from what we get in this story from Mr. W.: it turns out that Mr. Wickham was going to beat up on a blind stable boy, so Mr. Darcy had to take him out. Bang. Pow.
Basically, this is Mr. Wickman's M.O. He's just like his sociopathic Austen counterpart in that he's charming and personable but also a totally dishonest jerk who will do whatever it takes to get ahead.
How handsome does he look in his red coat now, Mrs. Bennet?
The good news is that Mr. Wickham really gets his comeuppance in this version of the story. When Mr. Darcy finds him in London with Lydia, he beats him to a pulp and then says the dude was in a carriage accident. The result: Mr. Wickham has to spend the rest of his days ministering to other disabled people at St. Lazarus Seminary for the Lame.
That's some poetic justice right there.