Plagiarism, for those that don't know the definition, is claiming the use of someone else's work as your own. On a game such as this where you write your interactions with other people, the application for a character and the character description are two places in particular that plagiarism isn't allowed.
When submitting an application the writing needs to be your own or used with the original writer's permission. While you can refer to a wiki as a resource on your character's traits and personality, the actual sheet entries need to be your own words. While you can reuse a sheet you wrote from another game, you should not copy from any source including another game, without the permission of the writer.
Everyone deserves to have ownership of their material. Using someone else's writing without their permission is theft, and if someone reports that to us we won't be happy. Consequences could include removal of characters from play, loss of characters, or more depending on the situation.