Warning: Spoilers ahead for "A Series of Unfortunate Events" books and Netflix show.
The book series "A Series of Unfortunate Events" is filled with sly literary references, wordplay, and other small hints that make reading the book — despite the unfortunate subject matter — a pleasant experience.
The Netflix television show adaptation is no different.
Daniel Handler, who wrote the book series, also wrote the script for the show. He imbued it with the same mischievous, detail-filled spirit. The first season adapts the first four of the series's thirteen books about the Baudelaire orphans (Violet, Klaus, and Sunny) trying to escape the clutches of the evil Count Olaf. The episodes include numerous references to characters, locales, and secret organizations we won't see until much later in the series.
Throughout the series, we see a mysterious insignia that pops up often.

The same symbol is a tattoo on Count Olaf's left ankle, on a spyglass Klaus picks up from his charred home, and in many more locations.

The letters "VFD" are hidden inside it.

"'V.F.D.' stands for 'Volunteer Fire Department.' It's a secret organization that puts out fires, literal and metaphorical, throughout the world that the Baudelaire parents, and many other characters in the show, were a part of.
The organization also has standardized secret codes used throughout the series, many of which are also referred to with V.F.D.-initialed phrases, like "Valley of Four Drafts" and "Veiled Facial Disguises."
Lemony Snicket references the V.F.D. early in the premiere when the Baudelaire orphans learn of the fire that destroyed their home and killed their parents.
"All that my associates and I have been able to learn is that neither the official fire department, nor the Volunteer Fire Department, arrived in time to stop the blaze," Snicket said.
You can read more about the V.F.D. here.
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