Riddle #1243

Question: Walk on the living, they don't even mumble.
But walk on the dead, they mutter and grumble.

What are they?

Question: What fish only swims at night?

Question: What do you call a mad elephant?

Question: What kind of mouse does not eat, drink or even walk?

Question: What has a bed that you can't sleep in?

Question: Where do all the letters sleep?