The SKIMS founder, 40, and the Good American designer, 36, were investigating who was behind Nori's Black Book Instagram page, a hysterical account written in the voice of Kim's eldest child, North West.

Who could it be? The SKIMS founder, 40, and the Good American designer, 36, were investigating who was behind Nori's Black Book Instagram page, a hysterical account written in the voice of Kim's eldest child, North West.

The clips opens with Khloe in a white top and black blazer as she adds massive silver hoops and very long nails; her hair is in a semi top knot and she has on neutral makeup.

'Are you behind Nori's black book,' she asks Atkin during Facetime as the hairstylist says no and adds she wishes she were that funny.

'No, I would die if it was Steph,' says Khloe as Kim says yes she would die too then looks at her cell phone.

'It's so accurate, it just has to be someone in the circle.' 'Are you behind Nori's black book,' she asks Atkin during Facetime as the hairstylist says no and adds she wishes she were that funny.

Ready to learn more: Khloe is dressed in a white top with black blazer as she flashes long nails.

'We have a serious question to ask you, are you Nori's black book?' asks Kim.

'We have a serious question to ask you, are you Nori's black book?' asks Kim.

Steph, who is a white tank top, says she wishes she was behind Nori's black book?

'Oh my gosh, I wish I was f**king Nori's Black Book!' Stephanie says!

Then Steph says she doesn't think the writer is any of the Kardashian friends because none of them are that funny, no offense, she adds.

We need help: Then in a confessional Kim says she called Tracy and adds Tracy always knows what to do.

Then in a confessional Kim says she called Tracy and adds Tracy always knows what to do!

In a hilarious turn, Nori's Black Book shared the KUWTK teaser with Kim and Khloe on Tuesday.

Mommy and Auntie KoKo are trying to figure out who is "Nori's Black Book".

Tune into Thursday's episode of @KUWTK on @eentertainment to find out who is behind "Nori's Black Book"