Kim Kardashian Reveals She Wore X-Men Outfit to Birthday Dinner That 'Wasn't a Costume Party!'

Kim Kardashian/Instagram Kim Kardashian and Tracee Ellis Ross

Kim Kardashian's X-Men-themed Halloween costume was not exactly part of the dress code at Tracee Ellis Ross' 50th birthday dinner on Saturday night.

But The Kardashians star, 42, was not above admitting the hilarious fashion faux pas on her Instagram Stories.

"That time I showed up to a birthday dinner in full costume when it wasn't a costume party!" Kim captioned a photo of herself dressed as Marvel heroine Mystique alongside Ross wearing an elegant crimson party gown. "Happy Birthday to the most beautiful kind soul @traceeellisross."

Later, the SKIMS mogul uploaded a gallery of images showing her dressed as Mystique alongside the simple message "Happy Halloween."

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Kim Kardashian/Instagram Kim Kardashian as Mistique

Kardashian's dramatic take on Rebecca Romijn's X-Men mutant involved dressing in a blue latex bodysuit, teamed with prosthetic bumps, electric blue face paint and bright yellow contact lenses.

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To complete her transformation into Romjin's shape-shifter, the mother of four opted for blue stilettos and slicked-back hair — which she dyed red for the occasion.

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Kardashian has used Halloween to channel multiple other notable figures over the years, including Vogue's Editor-in-Chief, Anna Wintour, Baywatch star Pamela Anderson, and Carole Baskin from Tiger King — for the latter, wearing a leopard-print top and purple floral headband while her kids dressed as Tigers.

Kim Kardashian/Instagram KIm Kardashian and Mystique

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Kim has also teamed up with eldest daughter North, 9, for matching Princess Jasmine costumes.

Kim's brood also did not disappoint for Halloween this year. On Sunday, Kim shared a carousel of photos of each of her four kids — including Saint, 6½, Chicago, 4½, and Psalm, 3 — all dressed up as a string of instantly recognizable music icons, including Aaliyah, Sade, Snoop Dogg and Easy E.