And no, it didn't involve party poppers and a Colin the Caterpillar cake.
The reality star and model marked achieving 40 million followers on the photo-sharing app by flashing her boob for the world to see.
Pulling down her top in a racy black and white snap, the picture would have been considered totes inappropes by the Insta police if it weren't for the red X hovering over her nipple.
The 20-year-old told fans: "My favourite photo for all 40 mil of you. genuine happiness...taken by lil Ky."