On of the most remarkable "songs" on the album is not a real song. It is the end of "A Day in the Life" (where the sound of fading piano chords were electronically prolonged to create an abnormal sustain) and that runs over in a 15 kilohertz tone that was designed to "freak your dog out" as John Lennon put it. Complete with laughter and gibberish, the "song" was then put in the inner groove of the record (only on UK LP's) so that the song would loop on and on unless you had an automatic needle return on your record player.
When Sgt Pepper's was first re-released on vinyl, they had actually great difficulty recreating an "inner groove", and the first pressing of the CD didn't have the ending at all.
Future pressings do have an artificial inner groove, where the end of the song is repeated a couple of times to create the idea of a "loop".