Marius Pontmercy

Marius Pontmercy is one of the protagonists of Les Misérables. He's a bit of a dunderhead.

Character History
He's a classmate of Les Amis de l'ABC and occasionally assists them in their revolutionary schemes. He's from a rich family, but is poor himself and has very few friends. He's head-over-heels for Cosette, and upon her departure, finally makes up his mind about joining Les Amis, but only so he can commit Suicide by French Army. Naturally, that doesn't happen.

He's the same in the musical, except he's with the ABC from the start.

In Badfic
He's probably the fandom's number-one lust object, which means he faces Mary Sues of all kinds, including those possessing Eponine or Cosette.