Hahaha I sure did! So as a quick recap of the history of Errant, it's a very hard reboot of a comic called Fan Dan Go I made about 9 years previously, and Fan Dan Go was a reboot of FanDanGo, which was a reboot of an earlier attempt at a comic under the same name.
The Fan Dan Go versions of characters are... familiar but to an Errant reader, they feel wrong. Like they feel like bad bootleg versions of the characters.
(Also aaaaagh oh god this old art is so bad aaaaaagh
I've tried to pick out some of the least bad looking panels from the old comic for the sake of my own sanity. Believe me, most of it looks worse.)
So we have Rekki, who has changed the least overall, but used to have this tragic backstory where she was a child soldier who fought in a civil war and her personality was more cocky and abrasive. I kept her design pretty much the same for chapters 1-3 of Errant because it's kind of iconic and just toned down the colours a bit.
And Subo is still the peace-loving guy with a healing aura except it only worked on him, he didn't heal others, more like Wolverine. Also he was white, which feels so wrong now. His modern design communicates the "hippie" vibe a bit more clearly. Not sure why he wears a shirt like he's going to work in an office.

Juliet Ellis went by "Juu" in Fan Dan Go, rather than Jules, which feels so odd now. They were not nonbinary in that version (I'm not sure I even really knew the concept of nonbinary existed back then in like 2008 or something, I didn't even know I was gay.) Also "Juu" had these... weird animu hair antennae, which hilariously I did try to make work in very early design sketches for Errant.
This version was more morally ambiguous and came across less playful and more scary, like you never knew if she was joking about traps or not. Despite this, the character has always been a fan favourite and was even back then.
Interestingly in all versions before Errant of the story, Juliet's sibling was called Frederick, and he was dead. When working on Errant it just helped pull everything together and give Jules a reason to be in the story if Rekki and Sarin's mentor was their older brother.