theres a reason behind these characters not appearing, and i think the series would be a bit too cluttered if ANY of these characters were to appear. think about it...
homeschool winner: too many shows have a standard "nerdy" character, besides strong sad half fills this role
the ungraits: these guys look like little terrorists. im sure SOMEBODY would get offended by the racial factor and other unnecessary insinuations.
champeen: theres no need for a female homestar wannabe. why have the same character twice?
dijjery-doo: its funny when various characters do pranks at different times, the doesnt need to be an official prankster character. besides, can you even pronounce that horrendous name?
trivia time: a dog? seriously? besides the walrus in best caper ever and the bats in SBCG4AP: BOTB, has there ever or will be an actual animal from this universe? no. they just dont fit so well in the hr universe
preshy and rafferdy: ugh, i cant stand these kids (dont even get me started... but i will), they look like strong sad mutants, they have bad squeaky voice acting, etc. the most i could see out of these characters would be what used to be dangeresque 3. you hear about it quite a bit but never see it.
the hurricane: i really dont know what to say about this one, but she looks weird. err... weirder than most things in the hr universe. shes the closest thing to a new character the series could get due to the fact the was prepped for animation and everything.