High Quality Content by WIKIPEDIA articles! Timmy Martin is a fictional character portrayed by child actor Jon Provost in the long-running television series Lassie (1954–1973). Provost debuted in the first episode of the fourth season, "The Runaway" (1957), as the fictional foster child of farm woman Ellen Miller. Both the character and its portrayer were hits with the show`s audience. In the middle of the fourth season series star George Cleveland died unexpectedly and producers were forced to overhaul the show. Timmy was adopted by newcomers to the series Paul Martin and his wife, Ruth, who purchase the Miller farm.