The image is actually a hallucination forced on Aqualad, known to his friends as Garth, by occasional troubled trillionaire Mento/Steve Dayton, who’s stepfather to another Teen Titan called Gar. (There was also a team hanger-on named Gnark, just to confuse newcomers.)
This panel refers to the adventure in New Teen Titans, vol. 2, #20-21, published a year before, in which Wonder Girl had assembled a team mostly of former Titans. That means the Robin in Garth’s vision with the buck teeth and math textbook is the second Jason Todd—as no one has ever pictured him before or since.