Halloween may not be until Wednesday, but this weekend the stars started celebrating early with bashes all over the country!

Kim Kardashian revealed her holiday ensemble last night in New York City, where she stepped out in a "Splash"-inspired mermaid costume to her Midori-hosted bash. Sporting a blonde wig and a fishtail, Kardashian looked great.

Her boyfriend Kanye West and BFF LaLa Anthony were also in attendance.

In Las Vegas, newly-engaged Jwoww and Roger Mathews celebrated at Chateau at Paris ... where Jwoww actually covered up for once!

Instead of a racy and revealing look, the "Jersey Shore" star and her fiance dressed up as nerds. So cute!

Check out the gallery above to see more celebrity Halloween weekend sightings -- including an unrecognizable Adam Lambert and Lance Bass, Stacy Keibler, Hilary Duff, Jessica Alba and many more!

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