The description of how Fearne's appearance changes when she re-enters the Fey Realm had so much magic to it.
Here's Matt Mercer's description:
"When you look at Fearne, she's Fearne, but there's something different about her. Her features are sharper, her eyes are bigger and deeper, her ears seem to almost be longer, her limbs seem to be just slightly exaggerated. There's this otherworldly kind of air about her that is just unique. It's upsetting at a first glance."
The moment takes place in Critical Role's third campaign during the episode Ominous Lectures.