The Saphead was based on the tried-and-true Winchell Smith stage comedy The New Henrietta, previously filmed in 1915 as
The Lamb.
Buster Keaton, at the time a popular 2-reel comedy attraction, makes his feature-film debut in the role of the addlepated son of Wall Street lion William H. Crane. In an effort to make something worthwhile of his unprepossessing offspring, Crane gives Keaton $100,000 to buy a seat on the stock market. Keaton gets mixed up in a seemingly worthless stock, but proves at the end that he's got more business sense than all the other brokers combined. Surprisingly, The Saphead is almost bereft of slapstick, until Keaton forces the issue in a riotous stock-exchange climax. ~ Hal Erickson, All Movie Guide