Copycat Syndrome

When an internet troll can only think of one specific way to torment their victim online and that way involves stealing the username of that victim, or ripping off the username and stealing their gimmick, e.g if that person has a Deviantart account with a monster/horror theme and RPs as a werecreature, the troll will use that as the main gimmick (including claiming said character is his/her own totally original character).

"I'm not Dr Music. I'm my own original username/character Doctor Bloosic."
"Sounds like Copycat Syndrome to me."