How about the essence of stupidity, it may be more interesting to make the enemy stupid.
The last hot spot of the story (That's not enough for a climax.) Sister Blue deceived Gargamel and turned herself into evil. After reading it, I thought of a better reason: Gargamel has caught so many Smurfs, but it's not He really needs to catch the other half (his stupid IQ is really better than just accepting it, he should have such self-knowledge), including the blue sister he delivered to the door, he is not so interested (the artificial smurf may not be so so much magic essence?)
Then the reason is: Gargamel has captured half of the Smurfs, which makes the kind-hearted her into eternal pain, and there are only two ways for her to escape such pain, one is to rescue all her companions (This is what Gargoyle is most worried about, this kind of thing has happened n times), the second is to change himself back to the original evil blue sister (and also dispel Gargoyle's concerns),
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