Once upon a giggly afternoon ...

 Sydney has turned into a perpetual cartwheel machine.  I'll be walking past a room and see a blur of feet go by -- at eye level.  It's like I'm walking on the ceiling.  She cartwheels down the hall on her way to bed; off the deck onto the grass and back up; from the coffee table to the couch, etc.  You name it.  She'll cartwheel it.

Then, this buster has discovered the thrill of jumping.

 In the above version, he jumps up and lands flat on his bum.  A benefit of wearing diapers, I suppose.