"Never set a yak on fire"

The Grummles said this to me the other day.

So I ask you...WHY would you want to set a yak on fire?

It just annoys them.

Who enters a room and then swings a dead cat to see if there is enough space?...WHY would anyone be carrying a dead cat in the first place? I've never met anyone who kept a dead cat in his bag, just in case....

Me confused....