Carnivorous plants.

Depends on the size. Probably some sort of insect. Like ants or a beetle. If the plant is the type to swallow rats or large birds... um... A lot of beetles =) Unless maybe I was really annoyed with my cat and- wait, no. Not even then.

Time flies like an arrow. Fruit flies like a banana.

I BELIEVE flies are the cuisine of choice.

Whenever I can't think of what to write next, I have Gumsock blow something up.

You mean like a Venus fly trap? You can feed them bits of meat (not sure if it needs to be raw, but I'm pretty sure it'll digest what you give it), like from his lunch or from the refrigerator. If he's doing this on the sly (which I'm assuming because he has to have access to the stuff?), parents tend to ask questions when kids try stealing bits of raw meat, so he'd likely have the most access to things like... oh, hot dogs would be perfect. Little bits of hot dog.

That said, they don't really eat much. I'm sure an 8 year old boy would be really into feeding his plant, but once all the little "mouths" were chomped on something he'd have to wait until they opened again, I think. Which would take a while.

Also, apparently, don't feed it an M&M. It will take forever to digest.

I had a Sarracenia (North American Pitcher Plant) for a while, and fed it all the flies I could catch.
I think over-feeding is more likely to be a problem than under-feeding. To quote Wikipedia, "Insects may be fed to the plants by hand to supplement their diet; however, carnivorous plants are generally unable to digest large non-insect food items; bits of hamburger, for example, will simply rot, and this may cause the trap, or even the whole plant, to die." - so I hope mommy slaps your 8-year-old's hand if he tries to feed the plant his hot dog. ;-)

From the International Carnivorous Plant Society: http://www.sarracenia.com/faq/faq2440.html

Those who want to make dreams come true must dream deeper and be wider awake than others.
-Karl Foerster