Saturday morning pheenom

Can someone please explain this to me?
All through the week, we wake our kids up, dragging them out of bed for school. With much weeping and gnashing of teeth, they are forced to vacate the warm bed and get ready for school. The 7am wake from hibernation happens on monday, tuesday, wednesday, thursday, and friday.
And then Saturday arrives...

Well, let me back up for a minute...friday night, Melody and I put the kids down a little later than usual. And we preach the strong message to them that mommy and daddy would really, really like to sleep in tomorrow morning. This is NOT a school day...it is called lazy-saturday. "So, kids, mommy and daddy would really appreciate it if you would sleep...like you do every other day of the week...sleep, dear children. And may God bless you and prosper you and increase your territory. Amen." With that, they are placed in bed with dreams of saturday morning SLEEP.

And then Saturday arrives...

You know what happens...all the best made plans of mommies and daddies are awakened to the cry of "I'm awake". Melody and I look at each other and all we can muster up is "NO!!!!!" Our hearts are crying out "God, where did we go wrong?" Both kids wake up, on their own, much earlier than any other day of the week. They are energized and ready to embrace the day.

What is it about saturday that puts this wild streak in our children?
Are they trying to get us back for something?
Can we just get some sleeep?

Can someone please explain this saturday morning phenomenon to me???????????????