J.K. Rowling - Harry Potter and the Order of the Phoenix
Chapter 28: Snape's Worst Memory - Page 570-571 (Aus/NZ Ed.)

But too late, Snape had directed his wand straight at James. There was a flash of light and a gash appeared on the side of James's face, spattering his robes with blood. James whirled about; a second flash of light later, Snape was hanging upside-down in the air, his robes falling over his head to reveal skinny pallid legs and a pair of greying underpants.
Many people in the small crowd cheered; Sirius, James and Wormtail roared with laughter.
Lily, whose furious expression had twitched for an instant as though she was going to smile, said, "Let him down!"
"Certainly," said James and he jerked his wand upwards; Snape fell into a crumpled heap on the ground. Disentangling himself from he robes he quickly got to his feet, wand up, but Sirius said, "Petrificus Totalus!" and Snape keeled over again, rigid as a board.
"LEAVE HIM ALONE!" Lily shouted. She had got her own wand out now. James and Sirius eyed it warily.