Supermodels just want to have fun, and dress up as Jessica Rabbit.
Before arriving to the celebration, the runway veteran documented her hair and makeup routine on social media. With help from makeup artist Vincent Oquendo and hairstylist Bridget Brager, Alessandra was able to transform into Jessica Rabbit from the 1988 film Who Framed Roger Rabbit.
Complete with purple gloves, a red wig and a dress that revealed plenty of leg, the supermodel turned heads for all the right reasons.
"Ready to party, woo," she shared on Snapchat. "Happy Halloween 2016."
Joined by her fiancé Jamie Mazur and close friends, Alessandra was spotted dancing to "Sorry" by Justin Bieber and "Baby Got Back" by Sir Mix-a-Lot during the star-studded bash.
Derek Hough, Ryan Seacrest, Molly Sims, Leonardo DiCaprio and more stars were also spotted at the annual event.
While Alessandra deserves plenty of credit for her costume, we can't help but be reminded of Heidi Klum's rendition back in 2015.
During her holiday party at Lavo in New York City, the America's Got Talent judge nailed the look from head to toe.
In fact, the Project Runway host began preparing for her costume with the team at Prosthetic Renaissance weeks in advance.
What will Heidi be this year? We will find out when she hosts her annual party at Vandal in New York City this Monday night.