Art Evolution: Hella Jeff's appearance here◊. Actually, it's more like Art Devolution in this case. In addition, the comic's policy of saving in JPG and copying over parts from previous comics causes artifacts to gradually build up, meaning that each character pose gets worse the more it appears.
Author Appeal: An in-universe example: Dave clearly emphasises the rumps of characters in SBaHJ. Dave's Bro, whom Dave strives to emulate, appears to have an odd puppet-ass fetish.
Fan Disservice: If it's even vaguely intended to be sexual, it's this in spades; sexualising anything with this much Stylistic Suck makes it infintely more disturbing to regard. Even stuff that isn't presented in a sexual light but is nonetheless emphasised is this; we're talking a comic which put heavy focus on an elelephant's HUGE BUTT and GREY MUTANT PENIS◊.
And issue 44 features a close up on a bull's ass. Then it takes a shit.
Issue 47 features a close up on Hella Jeff's ass taking a shit. Into Sweet Bro's pipe.
SB donf lik to be SEEN as furbeh, those. f YOU Look at the boffom of thE paig, the cOMic name i bube just no???
Fonts: It's lettered in Comic Sans, which, true to form, is considered pretty terrible to read.
Fountain of Memes: In-Universe. The whole reason it was brought into Homestuck was to provide a source of memes that would be original to the comic and exclusive to the characters. (It's also one in real life, of course.)
Gag Penis: The elelephant, with its GREY MUTANT PENIS.
Gambit Roulette: "the short... GLOWNS IN THE DARK / the short acutally DOES NOT GLOWN IN THE DARK / too find out watch thing is true...... BUY THE SHIRT????" The first run did not glow in the dark. The second run did. Then the same thing happened again with the second and third SBaHJ shirts.
"... The thing is, some of those new shirts got mixed in the the old ones. So I guess if you order one there is still a CHANCE you will get one that doesn't glow in the dark? So really the offer stands as the wild card originally advertised."
Jerkass: Hella Jeff, who loves screwing around with Sweet Bro as much as he can, usually for his own amusement.
Karma Houdini: Hella Jeff. He steals the car, bangs Sweet Bro's mothernote something Sweet Bro has also done, and is an all-around douchebag.
His punishment is having to put up with Bro's incompetence.
Lampshade Hanging: There's now a space for advertisements on SBaHJ, which feature the remark below "(i hope the ad is for some ponography!", seemingly hanging a lampshade on the fact that most of the ads on MS Paint Adventures proper end up being for porn comics.
Living Prop: Geromy, despite getting a formal introduction in big letters. He doesn't even move.
Long Pants: Hella Jeff and Geromy are always wearing these. Sweet Bro actually had differentiated pants at first, but is now always drawn with these.
Loophole Abuse: After being corrected during a chess game, Sweet Bro throws a pawn in the toilet and declares checkmate.
Parental Incest: The punchline of the second comic (which was actually the first one made). The psychological repercussions are not explored.
Poe's Law: An in-universe example: in Homestuck, it's described as "a webcomic ironically maintained through a satirical cipher" with "legions of devoted fans, most of whom are totally convinced" of Dave's sockpuppet persona's sincerity.
Then you realise that SBaHJ really does have large numbers of devoted fans and is arguably more well-known than Homestuck...
It's hard to get more well-known than Homestuck, and in any case Hussie has said that HS references SBaHJ so much it's actually easier to read the latter without the former than the other way around.
The banner ad block is somewhat less lighthearted, riffing on the number of advertisements for porn comics which are an inexplicable regular feature on the main MS Paint Adventures website (well, and Oglaf...).
Two Gamers on a Couch: It initially sells itself as such, but quickly descends into madness. Very few comics have to do with video games, and even then only tangentially, and the only comic where Sweet Bro and Hella Jeff are actually on a couch playing video games quickly turns to... something else.
Wham Line: "i was banging your mom for a minute there...... AND NOW YOU ARE BANGING HER"
What Could Have Been: Dave originally planned to make Cool Dude and Stoner Lou despite regretting the fact that it looked too much like his brother's stuff. As part of her trolling and a stable time loop, Terezi's artwork inspires him to make SB&HJ.
Word Salad Humor: "WHAT'S IS that guys even his PROBLEM? is like heg got BROAD SIDE SCHOOL FED up the BONE BULGE"
This is revealed eventually in Homestuck to be something Dave quoted ad verbatim from Tavros's early trolling attempts, presumably not knowing what it meant (he uses it out of context and incorrectly) but thinking it sounds funny. At the time he said it, Tavros was adopting a Totally Radical rapper persona in the hope of besting Dave, which was making him harder to understand. It also later turns out "schoolfed" is the ordinary troll term for 'schooled', and a "bone bulge" is a phallic troll sex organ of some kind.