All we have to do is make a sentence that never ends. So everyone has to add one word at a time, but copy and past the previous post into yours so we know what it says. The words do not need to correlate with the sentence, it makes it all the more fun to read.
Example: (a) Birds (b) Birds ...are (c) Birds are ... noisy (b) Birds are noisy ... bananas (a) Birds are noisy bananas ...fried