You know those paper families you cut out?
Well, I put one of those in an orphanage.
Listen up, genius. You see, the joke is that the author, probably an orphan who created a paper family (a family made out of paper), decided to put it in an orphanage. The joke relies on the irony and dark humor of placing a symbol of family in a place where families are absent. It's funny 'cause it's messed up, you dig?