All the Mutable signs – Gemini, Virgo, Sagittarius and Pisces – do this to a certain extent but Pisces has turned it into an actual complex. We need to think of a name for it.
Basically, it is that thing where Pisces presents whichever aspect of their self they think will be the most apt for the occasion or person in question. They have a huge drop down menu of different vibe & personae.
Depending on the moon phase, their human growth hormone levels, the atmospheric pressure and/or the dreams they had last night, they will either keep that character/performance fairly low key or they will ramp it right up.
If you want a quiet scene to go loud as fuq for no reason, call in a Mutable.
But then, periodically, Pisces/the Mutable person goes absolutely ape-existential due to not being understood.