As the series continues, the films become a lot darker and a lot more serious which is why any comedic relief is greatly appreciated by viewers. So when Harry drinks some Felix Felicis in an attempt to retrieve the memory that professor Slughorn is concealing from Dumbledore, Radcliffe's performance changes from broody teenager to baked college student. Harry becomes loose, optimistic and quite frankly, acts a little high. It's branded as a WTF moment because it's such a transformation from his usual, serious self. It's also supposed to bring you luck, not make you act intoxicated.