A mountain beaver is like a large rat, and lives along the western coast of the united states. It is generally brown has a stubby tail, beaver like teeth, and killer claws. Mountain beavers are nocturnal and are difficult to find, like yeti's.
Katrina: Dude what was that
Marina: It was the beast of the forest, a Mountain Beaver
Katrina: It looked fierce, I wouldn't want to go one one one with one of those!
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.