Played by the soundman Roger Giguère, he is an invisible character who interacts with the clown Patof through sound and music effects.

[2] Lesley Tranquille (a play on words meaning "leave him alone") quickly captures the hearts of children.

The song is credited to "Tranquille" to differentiate it from the TV character and is also included on a K-tel double-LP compilation called Disco Fever (1978).

The following season, a new series titled Le monde de Monsieur Tranquille (CFTM-TV, 1978) was created with a more educational focus.

However, the series was canceled midway through the season, largely due to competition with the highly popular Bobino on rival Ici Radio-Canada Télé, which aired in the same timeslot.