Remus had his head buried in a book and wasn't much aware of anything beyond the flowery script he was devouring with his eyes. Not too far away, Severus Snape was running his finger over the spines of books about sleeping draughts. If Snape wasn't so absorbed, he might have noticed the hardly steady bucket hanging in the air above his head. He might have heard Remus' warning; he might not have let out such a girlish scream as treacle was poured over his head. Remus, typically, went to Snape's aid. Sirius and James ran for their lives, fearing wrath.