Ha! Way back in Nightwing's first arc, I commented that someone should have noticed that Nightwing had a connection to Haley's Circus, when he cropped up in every city it visited. Turns out I was right. The Joker noticed! I feel smart.
Also, has it always been a thing that Nightwing has to get stabbed in every issue, and bounce back like nothing happened? It seems like it's been a trend for him since New52.