Turns out that no one actually knows. And that it differs for a lot of people. Some people, like me, feel lethargic and unable to do anything after sleeping for too long. Other people feel great when they get an extra few hours.
Some people say that it depends on whether you were sleep deprived, or not, when you went to sleep. A sleep deprived person supposedly feels good after a longer nap. Someone who hasn't been sleep deprived would have disrupted is circadian cycle unnecessarily. And so stuff happens.
But what about people who have insomnia. It's not exactly their fault that their circadian cycle is totally messed up. Sometimes even if I'm tired, I lie awake for hours thinking "okay, I have 6 hours left to sleep... Right, 5 hours. Four and a half..." and then I oversleep and wake up at noon or so.
Even though I have gotten about eight hours of sleep, more or less, I still feel horrible when I wake up in the afternoon. Maybe it's waking up to the midday heat. Maybe it's just that I look at the clock and go, agh, morning wasted. Whatever it is, it sucks.
So yeah. Why do I feel more tired after oversleeping, than before I slept? I'd love to take to an awesome pseudoscientific explanation and say that my mind is constantly working when I am asleep. (Hell, I'm sure that happens anyway) But I'm was leaning more toward the development of psychic powers and such...
Anyway, it's just been blazing for three days straight. This morning, the gods themselves were taunting me by producing a light shower. I thought it was going to get heavier and cloud the sky, bringing back the grey storms that I love so very much. But it didn't. Instead, it made me hurt my eyes and sweat more as I squinted out of the window to make sure it was really raining. Mind you, I can't remember the sun ever being so bright. It was like there was a solar flare directly in line with Singapore.
Also I've just been informed by my mother that I have some churchsy thing to attend on Thursday. That sucks, since I'm supposed to be doing stuff on that day. Doing stuff. STUFF. Stuff is important.
I don't have the energy to go into a "why religion is bull" right now. Gandalf.
Okay. I don't really have the energy to do anything else. So here's a .gif for everyone to amuse themselves with.

Watching people brain themselves, intentional or not, is always entertaining.
-Joe