If Harry had not seen Dudley’s lips move, he might not have believed it. As it was, he stared at Dudley for several seconds before accepting that it must have been his cousin who had spoken; for one thing, Dudley had turned red. Harry was embarrassed and astonished himself.
“Well… er… thanks, Dudley."
Dudley held out his large, pink hand.
"Blimey, Dudley,” said Harry over Aunt Petunia’s renewed sobs, “did the dementors blow a different personality into you?”
“Dunno,” muttered Dudley, “See you, Harry.”
“Yea …” said Harry, raking Dudley’s hand and shaking it. “Maybe. Take care, Big D.”