The SKIMS founder turned up as Mystique from the superhero franchise – alongside her pals Olivia Pierson, 33, and Natalie Halcro, 34, who dressed as Magik and Selene, respectively – without realising the “Blackish” star hadn’t mandated a dress code of fancy dress.
On a selfie of her in her blue body paint and red hair and the birthday girl in a glamorous red outfit, the 42-year-old reality TV star wrote on Instagram on October 10: “That time I showed up to a birthday dinner in full costume when it wasn’t a costume party!”
Kardashian also wished many happy returns to Tracee – who is the daughter of the Motown superstar Diana Ross – labelling her a “beautiful soul”.
She added: “Happy Birthday to the most beautiful soul @traceeelliseross.”
“The Kardashians” star also posted a snap of her and and hip-hop mogul Diddy, 52, in his Halloween costume, the Joker.
She wrote: “Never broke character.”
Kardashian also showed off her 9-year-old daughter North’s costume, a detailed alien garb that the little girl had dreamt up herself.
The 42-year-old star – who also has son Saint, 6, daughter Chicago, 4, and son Psalm, 3, with her ex-husband Kanye West said: “North came up w these prosthetic design.”
Kardashian had earlier delighted fans when she showed off her costume for the first time, with her donning a skintight blue bodysuit with a scaly finish to portray the shapeshifting assassin.
The former “Keeping Up With the Kardashians” star completed her transformation into Mystique – who has been played on screen by the likes of Jennifer Lawrence and Rebecca Romijn – with blue face paint, bright yellow contact lenses and a red wig.
In a clip shared to Instagram, she said: “It looks really cool like this."
Kardashian later shared a video to Twitter, which gave a shout out to Marvel and prompted fans to urge the entertainment company to “make it happen”.
Another fan praised the effort Kardashian had made.
They wrote: “Can’t imagine how hard you had to get into this costume. Reminds me when you starved yourself for Marilyn Monroe dress. Always going all out.”