Sometime around 2002-2003ish (maybe earlier), there was a thread where someone was talking about their beeper, but they misspelled it and said beeber (later sometimes alternated to beiber). In the responses, someone said they were stunned, but intentionally misspelled it as "stuned." From there it took a life of its own, and beebers/beibers were stuned on a regular basis.
The shower thing came from someone saying they were going to go take a shower, and to ping them if anything exciting happened. IIRC that was back in the Monica Lewinsky era, but yeesh, that's almost 30 years ago and my memory ain't what it used to be.