Yo dawg, i heard you like periods / so i put a period after your period so you can bleed while you bleed
A xzibit-yo-dawg meme.
Xzibit Yo Dawg is rapper Xzibit, host of MTV's Pimp My Ride, a show that put things inside other things in cars. The meme jokes about that habit: "Yo dawg, I heard you like X, so I put an X in your X so you can X while you X." It's the meme for recursion and anything that goes one level too deep.