Craziness at bedtime

So...at night recently, we all crawl into my bed after bathtime and read books for a while before the girls go to bed.  It is pretty much my favorite time of the day.  However, the past two nights, the girls have been super hyper and have done this literally as I was telling them to go into their room...not sure where the weird headbanging came from.  It started with Leah calling her PJs "MeeJays," which both girls thought was HILARIOUS and then they started what you see in the video...very strange!