A phrase used when one is baffled at how something is constructed or designed or an action that defies logic or general common sense. The phrase can be extended to anything that is non-sensical in nature. The phrase can also be used by itself when observing an action that prompts one to state "say you were smart" in a bewilderment state of mind.
Say you were smart and you designed this cheese grater that rusts when you put it in the dishwasher; observing a person swim in shark infested waters might prompt someone to state "say you were smart"
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.