The thing that makes this clip even funnier, is that once Peter Kay has told you what you are about to hear, that's exactly what you do hear. Even if you know the correct lyrics.
I've previously said on here that when i first began singing along to Dylan's 'Lay Lay Lady', i had convinced myself he was following those 3 words up with, "Lay across my big brown spade." I never really wondered why it didn't make any sense - i just thought it was Dylan being Dylan :-) Of course, when it was pointed out to me what he was really singing, that made much more sense.