If one side has one, the other side has to get one. Once launched, they cannot be recalled. When they land, they screw up everything forever.
or
Because he was feeling crumby.
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Shamboo!
Frankenstein: Witch can you make me a lemonade?
Witch: Poof you are a lemonade!
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Nearly unanswerable, since the one who tries to change it usually drops it, and the others call for a planning session.
or