Vyvyan Basterd
Adventurer
Why shouldn't it be a catchphrase used just by the villain of this episode? It is basically what he was trying to accomplish, after all.
It seems unlikely to me because the villain overused it. That would make him rather repetitive for no reason. We'd "get" the catchphrase after one use. Usually that sort of thing comes up over and over, like "Bad Wolf", when it carries greater meaning.
It could be that (what?) Moffat was showing how (what?) ironic it is for (what?) a being known as (what?) the Greater Intelligence to (what?) be as thick as (what?) a pro wrestler babbling (what?) out his catchphrase repeatedly (what?).