There’s also:
Jon’s mother - she shows up in many branches although tends to have even more variation than is normal for the other quasi-canon characters. The most common name for her is Linda from what I can recall, however this isn’t always the case. Her profession varies between storylines as does her marital status. In many branches it’s her father who is the grandfather that gave Jon the stone. It’s fairly common for her to find the stone and make an accidental wish while doing housework.
D Lettman - the only emo at Jon’s school and sometimes even the whole town. Name is usually Derek or Damian (I’m unsure whether the latter is down to me misremembering his name when I’ve written some branches or if it was an existing variation beforehand). Tends to have few if any friends and is usually picked on. I also believe that in most branches he’s either gay or at the very least ‘fag’ is one of the insults the bullies hurl at him.
Becky - older character that doesn’t show up much any more. In older storylines she’s Jon’s older sister. May be mistaken but I believe she was mostly used before Zoe and Mikey became popular characters for writers/readers.
Fred Orr - minor character that generally only shows up in Mikey focused stories. He’s Mikey’s bully and is usually the first person Mikey uses the stone on (except when it’s Jon first).
Joesph and Matt - characters that infrequently show up, but do recur from time to time. Fairly generic, they tend to show up only when the story needs non-Karyn friends for Jon if one of the bigger name quasi-canon characters aren’t already filling that role somehow.
Leonard Drullers - the other major geek/nerd character. Usually depicted as overweight (contrast with Jay who I believe is usually described as skiny/weedy). Some writers also give him personal hygiene issues to make him more unpleasant.
Sarah’s Parents - tend to be wealthy and her father is usually depicted as running McMillan Industries (presumably a major local business, although what they do is rarely if ever brought up), and her mother is usually depicted as being a middle-aged version of Sarah (with common backgrounds being ex-high school cheerleader and a career model).
That’s all I can think of off the top of my head.
