I first started writing this theory out back in 2019 after seeing a lot of versions of this theory that don't really represent DID correctly as a disorder or explain it well, so I wanted to try to present my version of this theory/headcanon while st...
S2 E6-7 "The Ultimate Enemy" S1 E15 "Fright Knight"
In "The Ultimate Enemy" Jack introduces the Booo-merang. The device immediately picks up on Danny's ecto-signature despite him presenting as human.
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Based on that we'd assume Danny's ecto-signature would be detectable at any time, but this isn't the case in "Fright Knight."
In "Fright Knight," Maddie has a device that picks up on ghost activity/presences, however it loses signal on any ghosts in the building Danny is in after he starts presenting human again.
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This leads me to believe that Phantom's ecto-signature is only detectable when he's fronting whether he's masking as Fenton or not, because the body understands he's a ghost and therefore must present as such in some manner.
Phantom was masking in "the Ultimate Enemy" and Fenton was fronting in "Fright Knight."
This would then mean that Fenton would have to full front for the system body to pass through ghost shields or to have the human "powers" in the ghost zone, seeing as the body would think it's a ghost when Phantom fronts.
