How do you make an orphan's hands bleed?
Tell 'em to clap until their parents come home.
Listen up, you dummy! This "joke" is dark as heck because it plays on the sad reality that orphans don't have parents. The punchline suggests they should clap until their parents come home, which, duh, will never happen. Thus, they clap until their hands bleed. It's messed up, I know, but that's the point!