Honestly, I had never heard the term "Mary Sue" before coming to this forum. If i'm not mistaken the term "Mary Sue" relies to a character who is essentially a super "fix all" character. She is the best at everything and whenever a situation arises that the heroes are unprepared for the mary sure character simply "gets another power" to take care of it. Essentially the character is ridiculously special and a cure-all for lazy authors. (The male equivalent is a Gary Stue or something like that I believe).
I don't know if this has been previously discussed but I think Cassie may be the exact definition of this character.
For example: she was the one who rooted them in time (can't recall what they called it) when they went off on their fantastical journeys, she was mysteriously immune to the disease Ax and the rest caught, she was a fantastic morpher, she single handedly started the yeerk peace movement, etc.
There were many more instances that I can't recall.
Does anyone have any thoughts or instances? Maybe a reason to disagree?