Kourtney Kardashian has been looking better than ever -- thanks to her non-stop revenge body work out regime. But even that can't keep her niece from falling down on the ground.

Kourt carried her daughter Penelope and Nori to ballet class on Wednesday but her squirmy niece would not stay put in her aunt's arms as they made their way into the dance studio on Wednesday morning. Eventually Scott Disick's ex put down the toddler and let her walk in on her own. She's getting so big!

Kourtney must have wanted to let her younger sister Kim, who turned 35 today, sleep in on her birthday. How thoughtful!

On the way out, Kimye's little lovebug tripped on her way out. It's possible the tot left all her grace and poise on the dance floor!

For the class, Nori was outfitted in a grey leotard and grey tutu. Penelope was dressed in a black leotard and white tutu. These two are tutu cute!

The 36-year-old mom of three wore a pair of skintight leggings and a tummy-baring crop top. Take that Lord Disick!