cook up

Tuzilishi
V + Adv (fe’l + ravish/yuklama)

to invent a story, plan, etc., usually dishonestly:

J. K. Rowling, Harry Potter and the Philosopher’s Stone 1 misol

Might this not all be some huge joke that the Dursleys had cooked up?
Ehtimol, bularning hammasi xolasi bilan amakisi uyushtirgan ahmoqona hazildir?