Below is the complete list of various characters mouthing others' lines in Harry Potter movies:
HARRY POTTER 1: - In the scene when Harry walks with his first letter into the kitchen and Dudley grabs it from him, then Vernon is saying about who would be writing to Harry. Dudley mouths his lines with Vernon.
- After the part when Harry says that his scar meant a warning, they all go to Hagrid who's playing a flute. Harry tells his friends about his suspicions and Hermione is mouthing his lines.
HARRY POTTER 2: - In the scene after Ron curses Malfoy with slugs, when he is on the ground and starts to cough up slugs Harry says about taking him to Hagrid's. Hermione is mouthing that.
HARRY POTTER 3: - In the end of the movie when Harry receives a broomstick from Sirius and Ron points at twins and says that they made him do it. Freds & Georges reply is mouthed by Percy who stands behind them.
HARRY POTTER 4: - After the second task, when Dumbledore is talking about Harry's results, Karkaroff mouths his lines.
- When Madame Maxim is talking to Hagrid about her horses' beverage, Crouch can be seen mouthing her words.