Explain the pun: biking without a helmet is a no brainer

What is going to happen to all that milk? " said someone. "jones used sometimes to mix some of it in our mash," said one of the hens. "never mind the milk, comrades! " cried napoleon, placing himself in front of the buckets. "that will be attended to. the harvest is more important. comrade snowball will lead the way. i shall follow in a few minutes. forward, comrades! the hay is waiting." in at least 100 words, why do the animals in animal farm refer to each other as "comrades"?