Naked Lad is a comic book character from the comic book of the same name, which is published in-universe of The Fairly OddParents.
The Timmy Turner apparently looks just like Timmy Turner, only ridiculously more muscle bound, with well defined pecs, abs, and a possibly sculpted butt, and is disturbingly very naked. The superhero's cry is apparently a scream, because when Timmy does such a thing when he realizes he's nude in public, he draws the attention of two nerds who want his "naked autograph". As Timmy makes his way back home in the nude, many more people mistake him for Naked Lad, usually causing them to crash into something.
Apparently, he is supposed to be a parody of Timmy Turner without his clothes, and with more hunky muscles.