Lyric: “I was a gobbling, dark night, robbing, joke’s on me, so serious.” In other words, he was a “Goblin, Dark Night, Robin” with a nod to the Joker's "Why so serious?" to sum thing's up.
Complex says: Double entendre abounds; and while Batman didn’t start out in video games, the Caped Crusader is certainly making a fine name for himself there.