I remember so many of them but there were the primary ones of course.
Christina was the main host and set the tone and had a good screen presence. Id give Allistair second after Christina left; he did well in that role. Kevin, Lisa was very popular and in a lot of skits but never really "led". Then you had Vanessa, Matthew, Kevin, and Doug who were always solid. I loved the rivalry between Doug and Vanessa.
Of course when it came down to it, the show's true unsing hero was Les Lye. From Ross, to Barf, to Blip, to Snake eyes, to the teacher/principal, to the father, to El Capitante, the guy did it all.

I remember Moose and Lisa especially. Not to take away from the rest of the cast but Moose and Lisa stood out the most to me.

The ones I immediately remember from childhood are Moose, Lisa, Alasdair, and Doug. (and of course Les)
Asps. Very dangerous. You go first.

Alasdair was the main guy on the show. there's no sorta about it. Lisa, Christine & Alasdair were the stars of the show.

I believe you there! Yeah the only cast I remember from the show when I thought about it were "Moose", Lisa, Kevin, Alisdair(sort of), Alanis Morrisette (only bc of her later fame), and Les Lye's various characters.
(Speaking of Les Lye, wasn't one of his characters the school cafeteria chef? Along with the comedic tone of the show, doesn't it seem like YCDTOT might've inspired a certain cartoon of today?)