Unless it's not Rhaegar, and this is a total curveball. George RR loves this shit. He made that fan theory seem pretty obvious right? It was guessed a long time ago.
Martin is all about the red herring... I mean, look at this Black Fish character? Black Fish? Red Herring? A character that seems to be really important and powerful and is going to be a big deal in the larger story, but whoops, he'd dead and never mind.
And Rickon... who names his dire wolf "shaggy dog." That's a reference to a type of story that seems to go on and on and ultimately goes nowhere
That's two... I'm sure there's dozens of hidden jokes he's planted in this thing for himself.