One fan said seeing Klum as a hyper-realistic invertebrate made them “feel sick if I look at it too long”
The supermodel (49) was unrecognisable under prosthetics that have horrified and fascinated fans.
"This is nightmare fuel,” one said, while others dubbed the disturbing giant worm outfit as “the worst and most horrible costume of the year.”
One Twitter user said seeing the hyper-realistic invertebrate made them “feel sick if I look at it too long.”
Others had mixed emotions, finding the costume “disgusting… in a good way” and couldn’t take their eyes off Heidi’s creepy transformation.
Some had trouble distinguishing what the model was dressed up as, with one mistaking the star for “a doner kebab.”
Heidi shared the layers and layers of prosthetics she had to put on before she reached her final worm-y form on Instagram.
"Almost ready,” she said, posting a close-up video of her looking completely unrecognisable with yellow contacts and startling features.
Heidi was dressed up for her annual Halloween party in New York, now in it’s 21st year.
"So excited to celebrate #HeidiHalloween2022 back in the Big Wormy Apple," she said on Instagram.
The German-American model appeared to don a couples costume with husband Tom Kaulitz who was dressed as a fisherman, holding a rod with his wife as the giant bait.
Speaking to Fox News Digital earlier this year, Heidi kept her costume under wraps until her shocking debut as a worm yesterday.
"I will be claustrophobic,” she conceded.
"I'm going to be really boiling hot, and it's going to be like hot in the club and everyone always wants to come and take their photo.
"It’s just a lot."
Heidi made a quick costume change later in the night, appearing in some glittery lingerie but keeping her prosthetic worm face – and fans couldn’t decide which outfit was more jarring.
In previous years, Heidi has transformed into Princess Fiona from Shrek, a zombie, an alien experiment and Jessica Rabbit.
Other stars making headlines with their costumes include Kim Kardashian, with the celeb dedicatng hours to becoming X-Men’s Mystique.
Kim later revealed however, that she got her wires crossed – and accidentally attended a dinner party as the only person in the room dressed-up.
"That time I showed up to a birthday dinner in full costume when it wasn't a costume party!" she captioned an awkward selfie with Tracee Ellis Ross.