Jennifer Lopez -- INSANE LAWSUIT -- Man Says She Begged Him for Naked Pics ... But It Stinks Like Catfish

Jennifer Lopez has been dragged into what looks like the craziest catfish debacle of all time -- a man just sued the singer, claiming she duped him into sending her naked photos in the mail ... but it appears a rando 53-year-old woman is secretly behind everything.

Rodrigo Ruiz filed the $10,000 suit against Lopez in L.A., claiming she sent him a letter in 2008 after he submitted a demo tape to someone he believed was in Lopez' camp. Ruiz claims Lopez demanded he reply with naked photos ... as well as more demo CDs.

He claims the letters led him to believe he had a chance at a music career -- and even a romantic relationship with Lopez, but she never followed through and he eventually gave up hope. Ruiz says he was so depressed he sought out professional help.

Ruiz sent us a few of the 3-line letters he received from "Lopez" and they're obviously bogus ... the first reads, "I just wanted to let you know that I do remember you and that I am interested in you. I have plans on leaving my husband. But I can't say much right now so that's it for now. Send me pictures of you both with clothes and without clothes."

Here's the second -- "This is Jennifer Lopez writing to you again and just to let you know that I got your packages, music, and demos. And just to let you know you need to send me pictures of you with and without clothes."

The third is the best -- "This is Jennifer Lopez and as you can tell its been a while since I last wrote and as you can see I have a new boyfriend which means your in for the long haul and you have to put up with the fact that I am f**king him and sucking his d**k."

In addition to the lawsuit, Ruiz filed a police report claiming sexual harassment.

Ruiz still believes Lopez sent these letters to him, but records show the P.O. box he replied to is owned by a 53-year-old L.A. woman.

We called her to ask about the lawsuit and everything else, and she nervously concocted a lame explanation about operating a Jennifer Lopez fan mail exchange ... and hung up on us.

A rep for J.Lo tells TMZ, "this is a small claims matter that appears to be a desperate attempt for notoriety. Ms Lopez has never seen or met the plaintiff, nor has she ever communicated with him. We believe this matter should be summarily dismissed."