Now, about Queen Elizabeth’s great-grandchild. Per Robert Davenport’s book “Roots of the Rich and Famous,” the infant’s grandpa, Prince Charles, is “a direct descendant” and, thus, William the pa is descended from Count Dracula. Drac solved Romania’s homeless problem by inviting them to a castle, then burning it down. Not really a nice dude.

Geena Davis’ family tree also has Halloween skeletons. She’s descended from those executed at the Salem Witch Trials. Ditto Lucille Ball, Walt Disney, John Wayne. However, scary horror type Lon Chaney’s dad was Gen. Custer’s barber, a pussycat. And Boris Karloff’s great-aunt Anna Leonowens inspired “The King and I” musical.

Brad Pitt’s snaggletooth “Fight Club” look was a hot ’99 Halloween costume. At great lengths for his career, he had some willing dentist chip pieces of his front teeth for the street-fighter role. Now rich, famous, unmarried and with a chorusline of kids, the teeth are repaired.

Robert Englund, Freddy Krueger in “Nightmare on Elm Street,” was in a limo, in full makeup, driving through a red-light district. He says: “One girl saw me — and I tell you — it scared her right out of the oldest profession.”

Linda Blair: “ ‘Exorcist’ fans still ask me to swivel my head around in a circle. They’re not joking. One sophisticate asked: ‘How did you get your head to swing around that way?’ ”

John Waters: “Not hard to look like me. With my slicked-back hair and pencil-thin mustache, I already look like a Halloween mask.”

Winona Ryder: “My high-school costume was a teenage Pussy Galore.” . . . Ellen DeGeneres: “As a kid, I carried around an actual lawn chair in a bag. The bag broke. The chair, too.” . . . Bebe Neuwirth: “One really cold Halloween, my mother made me wear a sweater. The harem dancer look did not do well with a sweater.”

A few lawsuits ago, Martha Stewart schlepped around as Bo Peep . . . High schooler Cameron Diaz as Kermit the Frog won first prize . . . Martin Landau: “I actually rang a doorbell dressed as Bela Lugosi.” . . . Fiona Apple’s favorite? “I once was a caterpillar.” . . . Christian Slater shaved his eyebrows to resemble Spock. They grew back oddly peaked.

George Clooney: “My best was as a milk carton. My face stuck out the side and the carton read: ‘Have you seen this child lately?’ ” . . . Mark and Donnie Wahlberg: Their sisters’ tutus.

They need a day

Oct. 31 is Nevada Day. In — ta-da! — Nevada. Celebrated with a street party. So, USA’s only city to celebrate All Hallows’ Eve on Oct. 30 is Carson City, Nev. May not come up in conversation. Also, you may not care — but I have decided to educate you.

If pumpkins are too scarce . . .

Another factlet: Celtics made the first jack-o’-lanterns. From turnips. Per Hamilton College historian Hans Broedel: If you can’t find a pumpkin, hollow out a turnip, carve it, hang it on a stick.

No costume needed

Jennifer Tilly: “I went as Cher. Everyone asked, ‘Where’s your costume?’ I thought I hadn’t needed much of one because I thought I looked like her.”

The night is one of feardom: Stephen King’s big fears. Reportedly, he’s hired guards to keep away trick-or-treaters. Rob Lowe’s memory? Tarted up as a baby in diapers . . . Rob Reiner? A clown . . . Noah Wyle’s nurse mom wrapped him in surgical gauze as the Mummy . . . Janeane Garofalo and Alicia Silverstone? Hobos . . . Steven Spielberg leaves trick-or-treat candy at his gate . . . Tom Hanks hands it out personally . . . As a child star, Jonathan Lipnicki’s professional help gave him otherworldly green makeup so he’d look like death.

***

Park Avenue. Woman wheeling a baby in a stroller. The pacifier had a black mustache on it.

Only in New York, kids, only in New York.