In an attempt to engineer a bit of Beano-style slapstick, I filled a bucket of water and rested it on top of the Biology classroom doorframe - and sat back to await the arrival of Mr Blissett.
Unfortunately, things quickly went awry on Mr Blissett's arrival, as instead of seeing him drenched, class 3G bore witness to him being knocked out by a full bucket of water falling but not tipping, cracking his forehead open on the floor as he crumpled under the weight. The water handily spilled from the bucket so as to wash up the blood from the spouting wound in his forehead, and I earned a one week suspension.
Fortunately, Blissett was back at work a week later with only his sense of humour badly damaged.