What is wrong with the money napoleon gets from Frederick on animal farm?

In George Orwell's "Animal Farm," the money Napoleon receives from Frederick is counterfeit, which ultimately leads to a betrayal and the loss of the animals' trust. This deceitful transaction highlights the theme of manipulation and the exploitation of the animals by those in power. Additionally, it underscores the consequences of naivety and the dangers of engaging with unscrupulous individuals. The incident serves as a critical turning point in the story, showcasing the failures of the leadership and the fragility of the animals' hard-won independence.