Why do kids do the opposite of what you want them to do?

Ever notice that, parents? When it's dinnertime and you want them to be hungry, they're not, but when you don't want them to be hungry, they're starving! The big one in our house is sleeping. Checked in with John before picking up the kids today to see what kind of a morning they had, so I'd know what I was getting myself into. He said they had a "slow, slow, start." He had to wake them up and drag them out of bed to leave on time. We did have a busy holiday weekend, so I figured they'd be tired today, but this seems like a recurring theme in my house...even for me! During the week, when we have to wake up early, we can't get out of bed, but then, on the weekend, when we don't have to get up early, both kids are up at the crack of dawn...wide awake! LOL! Me too! When I can sleep in, I can't, most of the time! What's up with that?

Please tell me this happens to you too! Please! LOL!