There are a few background characters in Les Misérables who never quite leave. Not just the ones who are associated with another character, like Valejan’s maid Toussaint, or the shopkeeper whom Gavroche bothers on several occasions, but characters who seem like one-offs, but come back anyway.
M. Bamatabois, the “gentleman” who attacked Fantine and precipitated her arrest, turns up on the jury of not-Valjean.
Boulatruelle, a local ne’r-do-well in Montfermeil, spends years trying to find Valjean’s secret cache of buried bank notes, taking breaks in between to help Thénardier out in his Parisian life of crime.
Village women on their way through the wood at first mistook him for Beelzebub and then saw that he was Boulatruelle, which was scarcely more reassuring.
Then there’s La Magnon, whom we never actually meet, but hear about on several occasions. She was once a servant of M. Gillenormand, Marius’ grandfather. A year or so after she left, she claimed M. Gillenormand was the father of her child. He took the boy in (arguing that he wasn’t the father, but that he’s perfectly capable of having been even at his age) until she blamed him for another baby, at which point he sent them both back, but continued to pay a stipend.
Even stranger: Her own two children died at a young age, but in order to keep getting her allowance from M. Gillenormand, she got the Thénardiers to give her their two youngest children, Gavroche’s younger brothers. A second round of arrests after the extortion leaves the two boys alone on the streets, where they run into the ultimate Paris urchin: Gavroche.
She disappears at that point, but it’s a long thread for someone who initially seemed to serve only as part of the background for another character.