The answer my friend is blow it out your end, the answer is blow it out your end

The story:

My mother (ex-hippie) had convinced my sister and I that these were the real lyrics as children. We had the record so I believed her. A few years ago, we were at a Bob Dylan and Paul Simon concert... he played the song and my sister and I sang along oblivious. My mother (and everyone around us!) started laughing so hard that she was crying.