I got this problem with my current roommate.  I’ll be watching mildly artistic “nature” films, and he’ll come barging in, and I’ll be sitting there just pounding away on a bag of chips, and I’ll be all like “hey mother fucker knock before you run in!” and then put away my ‘chips’.

And before you make mention of any locking of doors, I’ll tell you this.  My house was built when god himself was in diapers, and apparently the world was a safer place then, cause there isn’t a single lock on any of the inside doors.