Gregor Anwhistle, the brother of Isaac Anwhistle and brother-in-law of Josephine Anwhistle, was the founder of Anwhistle Aquatics, a marine research center and rhetorical advice service, located directly above the Gorgonian Grotto.[1]

Through a program called Volatile Fungus Deportation, he grew Medusoid Mycelium in the Gorgonian Grotto, and studied its poison for use as a weapon against the enemies of V.F.D. Kit Snicket warned Gregor that if he continued his research, great danger would come to the facility. The poison's antidote is revealed to be horseradish, or its culinary equivalents (which include wasabi).

Despite working on the noble side of V.F.D., Gregor's plans for the Medusoid Mycelium cause the Baudelaires to question his loyalties. Fiona suggests that Gregor was volatile, just like the Mycelium.

Gregor Anwhistle was killed in the Anwhistle Aquatics fire, which, according to the Daily Punctilio, was set by Fernald.

The Grim Grotto also mentions that Gregor was an ichnologist, a person who studies footprints.