It was the Cilla Black programme as BigTed said. A family were brought on the programme, shown what they would win (a prize for each member of the family, and usually quite big) if they completed the task. They then had a whole week to learn the task before performing on the next weeks show. All well and good if they did it, but if they didn't I used to feel awful for the kids who were in tears looking at the climbing frame/games console/holiday in Florida they would have won if only Mum or Dad had been up to the task. Dreadful programme.