This was fun to read. I liked guessing who the saboteur was and how the mystery was solved. The timing was very amusing! Most of all I enjoyed Harry and cat!Snape’s private moments. All that petting and playing and bits like this:
Snape lolled in the doorway on his back, his tongue hanging out and his eyes a little bit crossed. "What's wrong with you?" Harry demanded. "You look like an idiot." A sudden suspicion dawned. "That's your impression of me, isn't it?" he said, outraged.