<p>Gregory seems to have some paranormal abilities, such as truesight (he was suspicious of the witch's shack, and Lorna from the beginning), Conjuring (he only grabs like 5 or so leaves for a blanket but he suddenly has like 20 for both he and Wirt) and he was able to travel to cloud city.
</p><p>Also, I noticed that Jason seems to be able to do complicated un-frog-like tasks such as singing in English and he seems to mirror the spirits of Greg, that combined with the woodsman's advice about naming the frog and it seems to hold water.
</p><p>It could apply to Wirt as well given how they describe Jason as "Our Frog" and Jason seems to like Wirt well enough, not to mention that wit's revelation about the lantern is illustrated sith a ringing of a bell (much like the one inside of Jason).
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(Edited by Figwit2112)