The clouds of chimney soot which engulfs the boys and Jessup was actually powdered chocolate.
A different ending was planned but then discarded. Originally all three fell into the pool (Laurel, Hardy and the professor) and came out as chimpanzees.
While Ollie is working on the roof, a hill can be seen in the background with the number "57" on its face. This was an enormous advertisement, made of cement, for the Heinz 57 brand of pickles and other products. It was on the North side of the Baldwin Hills, to the SouthWest of Culver City, where the Hal Roach Studios were located. The colossal advertisement can be seen in historic photographs as early as 1916 (Huntington Library, San Marino, California, collection) and is also visible in other Hal Roach productions, such as the Our Gang short The Kid from Borneo (1933).
When Professor Noodle asks "Where's Jessup?" (his butler), Ollie says "Jesup? Oh, about 35 miles southwest of Augusta, Georgia." The town of Jesup is actually about 150 miles south of Augusta. But 19 miles west-southwest of Augusta is Harlem, Georgia, where Oliver Hardy was born.