MS Paint Adventures/WMG

Everyone Is Bi
All the detectives have shown at least some homosexual tendencies, while still falling for women:
 * Problem Sleuth has an unusual propensity for having Hunk Rump on his person, but loves Hysterical Dame.
 * Pickle Inspector is "homo-erotically interested in [his] fan", but is smitten with Nervous Broad.
 * Ace Dick married Wifehearst and had a child with her, but the Churlish Toff is known to watch Truffle Shuffles very intently.
 * Are you kidding me? When did the detectives start liking the girl counterparts? And the Churlish Toff is not a detective anyway.
 * The Churlish Toff is Gentleman!Ace Dick. Also, did you not see the Sudoku clearly labeled "beautiful dream girl?"
 * If that's the case, then DMK AND DMMK like Madem Mural despite no blatent interection aside from MK stealing MM's corset. Speaking of which that still doesn't explain where the concept of the detectives liking their female counterparts came from.
 * The entire existence of the female counterparts is, per Hussie's own comments, based on "deep seated mythology that dictates that any man secretly wishes to have sex with a female version of himself."
 * That doesn't mean they're smitten with each other. Sex can occur under any emotional circumstance, not just love.
 * Yeah, but something tells me  would not.

Death is Pickle Inspector.
They look comparable, and they're both nervous. Considering how many supernatural transformations PI undergoes over the course of the adventure, it's not unheard of that one of them would end up as Death.
 * It was told what all 8 PI clones became. None of them was Death, but 3 became dead.
 * Possibly, Godhead Pickle Inspector infused a part of him with the 3 dead clones, forming Death. And then Death was hurled into the past because of weird puzzle shit.

Pickle Inspector is the Wayward Vagabond.
The eyes look suspiciously similar, and the fact that he acts as a god-like figure in Homestuck, like PS's Godhead Pickle Inspector, just further enforces it.
 * He's way too short.
 * COMPLETELY Jossed probably a thousand updates ago.

The Prefectly Sane Man (the guy who marries wifehearst) is the protagonist of Jailbreak.
It would explain exactly why Jailbreak has No Ending. It lead off into Problem Sleuth!

All the MS Paint Adventures stories (With the exception of Bard Quest) are set within the Homestuck universe.
Alternia's Green Moon (Post-apocalypse) is shown to be where the Midnight Crew have been living a life of crime.
 * Now, taking the donation request stories as canon, the Midnight Crew were frequently antagonists to Problem Sleuth and his companions, meaning that Problem Sleuth was on Alternia's green moon (presumably the world that was real.)
 * On one occasion, however, Problem Sleuth and his fellows are trapped inside their offices, and adventure within an imaginary world separate from Paradox space (Where Homestuck/Hivebent take place). Within this imaginary universe, Jailbreak ends up happening, as can be seen here.

Andrew Hussie is the Anti-CWC.
Think about it. Andrew Hussie trolls the fans, while Chris' "fans" troll him. Chris almost never works on his comic, while for Andrew, pretty much his whole day is working on Homestuck. Where are they similar? They both stopped paying attention to pop culture around the year 2000.

Andrew Hussie
Actually MSPA is ran by 20 New-Age Nazis, and "Andrew Hussie" is acted by B-Movie porn star Johnny Eggdale. The real author of MSPA is ex-professional wrestler George Gray, also known as One Man Gang.
 * ...Also known as Mr Hc Fortan spouts random bullshit on other sites. Stick to deviantArt, why don't you?

Problem Sleuth and related characters were actually the game constructs of an entirely unrelated Sburb/Sgrub session.
They came from a session not really connected to the kids' or trolls' in any way; oh, let's just say some random 6-player session just because. The Midnight Crew from the donation request stories? They're Jack and his fellow agents, but they're different counterparts entirely who also just so happened to also be destined to become the Midnight Crew. They're just enemies with Problem Sleuth and co. instead of rivals with the Felt.