I hear you've been sleeping...

The story:

The very last time that Paul sings the words "helter skelter" in the
song, he sings them rather quietly, right near the end, just before
the music starts to fade. I always thought he said "I hear you've
been sleeping," but I recently listened to a separated track of his
lyrics without instrumental accompaniment: It turns out that he
says "helter skelter," which in retrospect makes more sense within
the context of the song.