Wogan, The Price Is Right, all the popular television programmes offer two shows: the one you see, and the one you don't - the 'warm-up', designed to put the studio audience in exactly the right mood for the main attraction.
'The warm-up man', said one famous comedian, 'can make a duff show good, and a good show brilliant.' So who takes on this awesome responsibility?
What are the tricks of the trade? And can it all go hilariously or horribly wrong?
Glyn Worsnip finds out - from the stars, the producers, and the warm-up men themselves. Producer IRENE MALLIS