Suefluence

Suefluence is the adverse influence a Mary Sue has on a canon character causing them to show out of character behaviour and do things they never would do in canon. It can also have an effect on Agents, particularly if they're not expecting it, and has caused Agents to turn on each other at times. For example, the first DIA story involved rescuing an Agent who had been shot by his partner, who had taken the Sue's side due to overexposure to Suefluence. It may be possible that Suefluence could turn an Agent or canon into a Mary Sue, but this has (fortunately) not been tested.