The Wire/WMG
David Simon exists in The Wire universe, but we never see him
In the show's universe, he's just a police reporter for The Sun who hasn't gotten into television yet. Hell, if Jay Landsman is a cop in-universe and out of universe and The Sun is Baltimore's main newspaper in both realities, why not? One major difference: in The Wire, David Simon is a buff, chiseled sex god who rides a motorcycle and works as a bounty hunter on the side. Because, y'know...when you're the creator of the show, you can do whatever you want.
Levy deliberately leaked Marlo's phone number
In Season 5, Maurice Levy obtains Marlo's phone number and very deliberately places it in his rolodex, right in front of a former policeman with a history in wiretap investigations, very carefully using the words "wiretap investigation". It seems unthinkable that the amazingly calculating Levy would do this without a purpose. Did he deliberately plant the idea in Herc's head to leak the number to his former colleagues, to create a profitable wiretap case as soon as possible? Hell, did he even figure that with the police (very publicly) so short of money right now, that the investigation would be shoddy and easier to win than most? And if he did, is he the finest chessmaster in Baltimore? It seems likely.
George Pelecanos uses the tears produced by the episodes he writes to fuel a genesis device
How many gallons of tears has he gathered over the years? Wallace's death, Sobotka's death, the end of Hamsterdam, all the kids in season four except for Namond getting their futures ruined, Michael losing his soul in season 5... it all adds up to a diabolical scheme for world domination.
Marlo Stanfield was molested as a child.
Possibly by the same culprit as Chris. The two seem to have a unique, unspoken bond and absolute trust between them (Chris stands guard while Marlo busts a nut). Chris and Michael are the other two characters on the show who are quiet and introverted, as well as terrifying individuals and ruthless killers. Both molested. And Marlo immediately seems to take a liking to Michael. Consider Marlo's shooting of the girl in Season 3, in which he puts a bullet in each tit and another in her mouth. On top of that, just watch his reaction to the rumor that he's gay, and maybe contrast it with Michael's outburst in which he accuses Cutty of the same, claiming "everybody's too damn friendly." A mindset like that could definitely lead to a personality like Marlo.