Kim stopped by "Late Night With Seth Meyers" on Tuesday, where she revealed that things got a little messy during the couple's family portrait with 9-month-old daughter, North West, shot by famed photographer Annie Leibovitz.
"North peed on him right at that moment," Kim said. "And he was trying to tell me, and I couldn't really hear him, but I had to get up and get her, clean her off, clean him off. It's a good memory."
However, Kim couldn't share that funny moment, or any moment from the shoot, with friends or family, since she was sworn to secrecy over her Vogue spread, which was hard for Kim, who admitted she has "the biggest mouth ever."
"I didn't know it was going to be the cover, and it was such a secret. I didn't tell my sisters; I didn't tell anyone. My mom knew because we had to use parts of her home, so it was this top-secret mission trying to keep out all of my sisters," Kim revealed. "They were a little suspicious, but I just said Kanye was shooting something at my mom's house and it was really private and just kind of blamed it on him."
Kim, who is expected to tie the knot with Kanye in May, described the Vogue experience as feeling like "the real life Carrie Bradshaw" from "Sex and the City."
Not everyone is as ecstatic that the two landed such an iconic cover, but that doesn't seem to faze Kim, who calls it an "honor."
"I know it's a first of a lot: They were telling us that Kanye is the first rapper to be on, and I'm the first reality person to be on and the first interracial couple, so all of this just means so much I think to Kanye and I," Kim said. "Every girl I think grows up dreaming they could be on the cover of Vogue, and I collected vintage Vogue's forever, and it's just honestly the biggest dream come true, and I'm so honored to be on the cover."