Harry Potter is such an immensely popular phenomenon that I'm amazed we didn't see more of it in the first Lego Movie, save for a short cameo appearance from Dumbledore. If Lord and Miller want to move away from superhero characters a little for the second film, Harry, Hermione and Ron would be a great substitution, given their massive likability factor, and how well the idea of wizards would mesh with Master Builders and the Lego world in general. The Harry Potter series may be over (seemingly for good, but we'll see), but there's still a huge audience gagging for more, and so this would be a great way to keep the brand relevant, and probably earn J.K. Rowling a few more bucks at the same time.