In the scene, Kim looked her normal self when a wet splotch developed on the right side of her shirt.
"Your boob is leaking out of control!" Khloé said, while Rob chimed in, "That freaks me out, for real!"
Ironically, it's not the first -- or even second -- time breast milk has been incorporated into a bit for the show, as episodes last year had Kourtney lending Kim some of her milk output to help with a skin-related issue; and Khloé tasting Kourtney's milk on a lark from Scott Disick.
Watch the video on RadarOnline.com
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As we previously reported, an insider told us last year, shortly after Kim gave birth to daughter North June 15, that the reality star was "having trouble" with the natural process.
“She has been telling friends that it is really hard, so we don’t know how much longer she’s really going to do it," the source said. "Kim is probably already plotting what she’s going to say when she stops."