Hubble, bubble, toil and trouble!
Thrillingly, this is the first time a blue moon has taken place on Halloween in all time zones since - wait for it - 1944.
What's more, trick-or-treaters won't see the next Halloween blue moon until the year 2039.
As you carve your pumpkins and stock up on sweet treats, be sure to set your reminders for a spot of sky gazing too, as this fascinating spectacle is not to be missed!
So, what is a blue moon?
Despite its name, a blue moon doesn't actually appear blue in colour - but it's mesmerising none-the-less.
According to NASA, blue moons occur once every two and a half years and are a phenomenon featuring not one but two full moons.
Usually, calendar months have only one full moon, but occasionally a second one will sneak into the cycle.
This rare, secondary full moon is christened the 'blue moon' - hence the expression, 'once in a blue moon'!
The phenomenon occurs because the lunar cycle and the calendar year are not perfectly synced. Full moons occur every 29 days, while most months are 30 or 31 days.
This year, the first full moon occurs on 1st October and is known as the Harvest moon, as it's the full moon falling closest to the autumn equinox.
The second full moon peaks on October 31st, bringing a thrilling dimension to Halloween and making spooky celebrations all the more special.
According to Earthsky, the Halloween blue moon "will appear full to the eye" from "around the world".
Given that we've already experienced a close encounter with Asteroid 2020 QG and witnessed the three-mile-wide Comet Neowise this year, it's a big year for sky watchers.
Happy gazing, earthlings.