It is best not to look too closely at Edvard Munch’s screamer at the exhibition “The Art of the Brick,” which opened this week at Discovery Times Square. Because then you would see that the head is pieced together out of beige and white Lego blocks, their studs protruding. Leonardo’s “Mona Lisa,” on display nearby, has a smoother surface, composed of 4,573 “bricks” (as they are called by aficionados), but you’d never mistake it for the original — the overall effect is more allusion than illusion.