How we cite our quotes:
"I am glad to see," she said, "that there are no slimy creatures in my drinking-water this time. If there had been, then something exceptionally unpleasant would have happened to every single member of this class. And that includes you, Miss Honey." (20.15)
When people play pranks on her, the Trunchbull becomes even more determined to be violent and evil. She just takes them as excuses that let her punish other people. She'd be mean anyway, but when someone plays a prank, that makes it even easier for her to unleash her violent side and lash out.