Cleveland Cavaliers star LeBron James dressed as Pennywise the dancing clown from the Stephen King book and film, "IT."
Kristen Bell dressed as Elsa from "Frozen" to match her daughter, though she voices Elsa's sister in the hit animated movie.
Demi Lovato gave fans a peek at her tribute to the late music star Selena Quintanilla on Snapchat over the weekend.
Credit: Snapchat/Demi Lovato
Jonathan Cheban and Kim Kardashian
"I got you, babe." Jonathan Cheban and Kim Kardashian transformed into Sonny and Cher for the Casamigo Annual Halloween Party on Friday, October 27.
"Winter is coming!" Singer Jason Derulo dressed as the Night King from "Game of Thrones."
Gwenyth Paltrow and her producer boyfriend, Brad Falchuk, made a throwback reference to Paltrow's 1995 film "Se7en."
Neil Patrick Harris
Neil Patrick Harris posted a photo of himself, husband David Burtka and their 7-year-old twins Gideon Scott and Harper Grace dressed as "circus curiosities."
Lauren Conrad dressed as Cruella de Vil from "101 Dalmatians."
"I almost always make my Halloween costumes from scratch — the process usually involves cutting, sewing, and a whole lot of tulle," she explained on her website. "But this year, I found myself with a little less time on my hands (I'm sure my fellow new mothers can relate … ), so I opted for a less time consuming costume."
Laverne Cox dressed as Major Tony Nelson from "I Dream of Jeannie."
"Live on the strip!" Nas dressed up as legendary comedian Richard Pryor.
Rita Ora dressed as Poison Ivy from "Batman" for the annual KISS FM Haunted House Party in London last week.
According to Floyd Mayweather, he was "Achilles from 'Troy' or Maximus from 'The Gladiator'" for Halloween.
Supermodel Karlie Kloss dressed as Marilyn Monroe.
The music duo of Andrew Taggart and Alex Pall spent a "night at the Roxbury" during Halloween this year, dressed as brothers Steve Butabi and Doug Butabi.
Usher channeled his inner funk to become Rick James for Kelly Rowland's Halloween bash.
Hillary Duff dressed as a bunny alongside her 5-year-old son, Luca.
Actor Will Poulter gave the people what they wanted, dressing as Sid from "Toy Story," and he used his platform to raise awareness for a good cause.
"I thought I should respond to the comparisons with Disney Pixar's biggest bully next door and go as Sid from Toy Story," he wrote on Instagram. "In addition to having a laugh at my expense I wanted to try and raise some attention for a cause I am an ambassador for! @antibullyingpro"
Jennifer Garner dressed as a "cat nap" -- fuzzy mittens included. "I'll be looking for one of these today. #icrackmyselfup," she wrote on Instagram.
A pregnant Jessica Alba channeled Juno MacGuff from the 2007 movie "Juno." Her friend, Kelly Sawyer, played friend and admirer Paulie Bleeker.
Nyadak "Duckie" Thot
On Instagram, model Nyadak "Duckie" Thot wrote that she was paying tribute to the "Jewel of Africa, Cleopatra."
"Just maybe I will finally wear blue and yellow spandex for my Halloween costume," Hugh Jackman hinted while posing with an off-the-rack "Wolverine" costume on Instagram.