One of the mighty questions that begs to be answered. What da dog doin? Why da dog doin it? Where da dog doin it? When da dog doin it? Where da dog doin it? How da dog doin it? Why are you here? Why are you reading this?
A phrase you can use around your parents instead of "what the fuck" and can be goofy with in public to annoy the shit out of them, works especially on teachers.
While our lifespan is the number of years we will live, our healthspan is the number of healthy years we will have and our sexspan is is the number of years we will continue to be healthy enough to continue having an active sex life.
A lighthearted reaction upon receiving disappointing news of some sort. Usually something that isn't a particularly a big deal, esp. when it primarily affects someone else - sort of a mild schadenfreude. Sometimes doubled or tripled, and possibly said in a sing-songy voice for added comedic effect to imitate a muted trumpet, which is how the meme originated.