so alot of people have had problems with mary sues, characters made up to insert themselves into the universe of whatever the RP is going.
OC, an original character.

now if you're like me, and rp'd years ago when it was the thing to do on chatrooms or DA (i haven't seen much lately granted im not active in the RP community for some time now) you'd know that alot of people's first OC's were basically mary sues. the person was an exaggerated, powerful version of ourselves that we made to interact with the characters or other OC's of the universe.
now you might say "yeah sure all OC's at first start like that but as you get better you should try to roleplay something that isn't at all like that character, or be more mature about it and be a better writer"
It's not always that easy for some people, and some people like the idea of using a Mary sue. If all parties of the rp ar having fun, who gives a damn if it is a MS.
and for those of you who RP as Character of the canon,  don't turn that character into you, try to keep to it's actual likeness.