In ‘X-Men: Kill or Cure’ by Jason Aaron, Iceman forced to face the shapeshifting Mystique when she takes his form to draw public attention, including his. Though he was confronting someone else, he was in effect facing himself too – both physically and spiritually, as he learns more about himself through his interaction with Mystique. Upon meeting her as his doppelganger, he says, ‘Any chance you could look like someone else for a while? Talking to yourself is said to be the first sign of madness.’ This reflected his discomfort in facing himself. Yet, when overcome, it could lead to greater sanity.
Related Articles (Doppelganger stuff):
Don’t Look Back
https://moonpointer.com/new/2010/01/no-totally-different-or-same
The Broken
https://moonpointer.com/new/2009/11/you-versus-yourself
Do You Like You?
https://moonpointer.com/new/2009/09/do-you-like-you