Toxic twosome!

Kim Kardashian and Julianne Hough both channeled their inner villain for Halloween by dressing up as Poison Ivy, the hot bad girl made famous by Uma Thurman in 1997's Batman & Robin.

PHOTOS: Kim's sexiest costumes over the years

The reality star, 31, donned a fire-red wig, super-high heels and an all-green, cleavage-enhancing mini-dress dripping with green flora for Saturday night's Midori Green Halloween bash at LAVO in New York City.

"The party is obviously with Midori," the liquor's spokeswoman told Us Weekly. "So I wanted to wear something green and I thought, what really is there to wear green? There's Tinkerbell or a mermaid -- and I wanted to be Poison Ivy. I like the red hair idea.

The Footloose actress, 23, also wore a red wig along with a green one-piece number with a corset-style top for a bash in Los Angeles.

PHOTOS: How Julianne Hough became a red carpet star!

"Halloween Costume Hint: Wearing my RED wig that I wore in Burlesque...but my character is from another movie!" she tweeted on Sunday.

Get more Us! Follow us on Twitter, Friend us on Facebook, Subscribe to Us Weekly