The audience were not told who the guest was, and when Peter Sellers comes in, there is an audible gasp before the applause.
On the day of recording, Peter Sellers arrived at BBC Television Centre, in the morning, for technical rehearsals. He left at lunchtime and did not return until close to recording time. In that period he had completely changed his appearance with a wig, make-up and false teeth. He stayed in his dressing room and the first time Hattie Jacques and Eric Sykes saw him was during recording when he walked onto the set in the first scene.