"Quack," said Harry Potter, as Madam Pomfrey worked to diagnose him.
Harry was sitting on "his" bed in the Infirmary, frustrated by the unusual speech impediment that he somehow had picked up. For once, this was not the Twins' doing.
Harry snarled, "I sound like a quack idiot."
In the Infirmary was Madam Pomfrey—this was, after all, her workplace—and the headmaster of Hogwarts, Albus Percival Wulfric Brian Dumbledore. Dumbledore's robes today were coloured teal, the colour of the sea, because Dumbledore felt that Hogwarts needed more teal sea (TLC).
Also in the Infirmary was Hermione Granger, who was worriedly wringing her hands. Not in the Infirmary was Harry's supposed "best mate," Ron Weasley, who was elsewhere because he had a more important task to perform. (Namely, playing Wizard's Chess against Seamus Finnigan in the Gryffindor Common Room.)
Harry said, "Please, Madam—quack—Pomfrey, tell me what the quack quack is wrong with me!"
Suddenly Madam Pomfrey's wand quit waving. She backed away from the bed, spun round to face the headmaster, and wailed in a voice of utmost despair, "I CAN'T SAY IT! DON'T MAKE ME SAY IT!"
"Oh no," cried Hermione. "My poor Harry!"
Hermione ran over to the bed and gave Harry the longest Hermy-hug she had ever given the green-eyed wizard.
Harry yelled, "SOMEBODY"—quack—"TELL ME WHAT IS"—quack—"WRONG WITH ME! I DON'T"—quack—"CARE WHO!"
The headmaster showed Harry his strongest "disappointed grandfather" face, even as his eyes were twinkling. "Harry my boy, you are going Duck."