I helped out with my mom's fourth graders every year when they did their talent shows- obviously, given the age and context, things had to be clean and kid-friendly. Some of the stuff we did:
- The kids acted out a rapped version of Green Eggs and Ham, sung by the a cappella group Moxy Fruvous. It's really funny, even for older kids (I found it when a college friend played it for me); we had a kid who played Sam I Am, a kid who played the guy who doesn't want to try the eggs, and other kids doing backup.
- A singing/dancing routine to the Weird Al song "Ebay" (a parody of that Backstreet Boys song "I Want It That Way"). Weird Al sings about all of the bizarre things people buy/sell on eBay- the kids had props and shared the lines. It was really well received by the teachers and other kids. There are a lot of really great Weird Al songs that have totally clean lyrics, good beats and are funny for use in talent shows and such. If you need ideas, looking through some of his stuff might not be a bad place to start.
- "The Presidents Song" - this one was from the cartoon Animaniacs (anyone else remember that?). They sing a short rhyme about every president of the U.S., in order. It was written in the '90s, so it only goes as far as the Clintons, but it's really straightforward to just write a couple of lines for Bush and stick them on the end. For this, each kid picked a president, drew a picture of them or something that symbolized them, and sang the lines relating to "their" president. Like Weird Al, there are a lot of great songs from Animaniacs that work well for talent show/skit-type stuff. There's a lyrics archive somewhere online if you take a look for it, and you can find a lot of them on MP3.