In issue 2 of The Defenders volume 4 (written by Matt Fraction), Red She-Hulk needed to be scared in order to revert back to her human form (Betty Ross). Dr. Strange whispers something in her ear to trigger the transformation.
We the readers aren't privy to what Dr. Strange whispers in Betty's ear, but she refers to him as "The Creep" for the rest of the mission.
I've read all of the first six issues of the series, and they haven't referred back to this incident yet. Do we ever find out what Dr. Strange whispered, or is this left up to our imagination?