You know... the one where Kim calls Kourtney the least interesting to look at, because she was being difficult about arranging their family Christmas card?
Yeah, it was pretty epic.
And while we know nothing could tear the sisters apart, it was probably one of the biggest fights we've ever seen them have. Even after the episode aired, the sisters were back at it on Twitter arguing about the whole situation.
However, now that a few days have passed, little sister Kylie Jenner has decided to ruffle some feathers and reignite the feud.
Kourtney posted a hot af photo of herself from Kylie's 21st birthdy party, where Kylie commented, "Happy birthday <3 <3 you're so interesting to look at."
Yeah, Kylie did that.