Years ago my step dad woke me up by blaring a recording of a real lion attacking at full volume in my bedroom.  Needless to say that my reaction would bring him great joy every time he told the story to others for years after.  I have to admit it was very funny, once I got my bearings, and that's why I appreciate all of these wake up pranks.

Some are a bit mean, but many are very funny.  This is not work friendly as people don't always censor what they say when they having the living daylights scared out of them.

Enjoy, and sleep with one eye open.