It was explained by the author that N4-T3 (Nate) of Bob and George, the Yellow Demon that was converted into a good guy, was an Expy of a guy named Nate with similar glass that was going to be in the hand-drawn comic that was originally planned.
Olivia, Tate, and Zoey from Weesh are rather obviously modeled on Alex, Riley, and Tristan from the author's earlier Angel Moxie. (Zoey is a teenager and Tate is a boy, but other than that...)
Lindesfarne from Kevin & Kell fulfills a very similar role to that of Samantha from Safe Havens: a kind, witty and intelligent scientist. Both were created by Bill Holbrook.
Bro's rapping vetriloquist dummy Lil' Cal in Homestuck shares a large number of traits with Franklin from Arrested Development, one of Hussie's favourite shows.
In Act 6, we meet the Alpha kids, aka alternate universe counterparts of the original kid's guardians, who share some similarities to the dead trolls. Jane Crocker shares many similarities to Feferi and is related to her by adoption, Jake English has similarities to Equius, Roxy is an odd mix of Sollux, Gamzee, and Nepeta, and Dirk is Equius and Rose.
Even Dozerfleet Comics characters are prone to this. Candi Levens of the Ciem Webcomic Series is in many ways an expy of Vaneesa Abiyoti from Stationery Voyagers: Final Hope. Both are in-turn expies of Juanita "Olive Kitty" Bines, a character from a 1997 short-lived short story collection titled Mechanical Conflict. They may have different ethnicities and differing levels of mortality, but they are quite easily the same character, for obvious reasons.
Final Hope is even worse: Laura Herrante is basically just a Caucasian version of Vaneesa, and ends up having the role Vaneesa would have fulfilled if not for having been offed by Astrabolo.
Masked vigilante Maelstrom is not completely unlike a certain mascot of a certain band.
