Sellers had been a struggling musician before the smell of the greasepaint took him over and among the many stories he told was one that, of course, had happened to a good friend of his. At one of their gigs a smartly dressed chap comes up to the bandstand with a young lady on his arm and asks them if the band can play That's What You Are. The pianist cum band leader, having never heard of it, looks through his book in a vain attempt to find it. 'I'm afraid I don't know it' he confessed. 'What?!' says the man incredulously. 'I'll tell you something, what's the country coming to when a band leader can't play That's What You Are?'
'Maybe if you sing the first couple of bars' said the band leader, 'we may be able to improvise.'
'Very well'' the man says, clearing his throat. 'Unforgettable - that's what you are.'