Where is all this energy coming from?

It is 9:45 pm and my child is still talking/singing to herself as she lays in bed. Maybe it has something to do with the huge chocolate chip cookie she had during supper at church tonight ... and then the ice cream she got in the nursery ... plus the goldfish she most likely got on top of that. Who knows? She has really just amazed me lately with her energy. She goes to a full day of school, yet comes home and is WIDE open. Then, even when she gets in bed late - say, around 9:30 pm, she is still rarin' to go. She has already summoned me to her crib twice since I put her down - once to cover her and once to "get this" as she held her hand up in the dark. I said, "What's that?" and she said, "Something from my nose." Precious.