Beetlejuicing is when one user posts a comment or thread on reddit, and another user with a username relevant to that parent comment or thread responds.
It is not beetlejuicing if the commenter does not respond "naturally." Summoning someone with /u/ or asking them a question about their username is not beetlejuicing.
The congresswoman from my district got caught Beetlejuicing her boyfriend at the local theater, but she had to finish him off in the car because they got thrown out.