I'm always trying to introduce the twins to high culture, and since they love baseball, I figured it was time for Abbott and Costello's classic Who's on First?  And thanks to YouTube we have this great skit readily available:

YouTube: Abbott and Costello -- Who's on First?, classic version

YouTube: Abbott and Costello -- Who's on First?, faster version

And here's a completely remarkable variatation; check it out:

YouTube: Who's On First? as written by Shakespeare

God bless YouTube.