The lock where the "Fish-Slapping Dance" was filmed had a much higher water level prior to filming. When it came time to actually film the sketch, the water level had lowered about five feet, meaning that Michael Palin really had to take a dive.
Celebrity appearances on Flying Circus were rare. Nevertheless, the "It's Man Chat Show" sketch in this episode features both Lulu and Ringo Starr. Ringo was an avid fan of the show, and had requested to appear (fellow Beatle George Harrison would go on to produce several films for both the Python group and individual members).
The Pythons did most of their own stunts. In this episode, Michael Palin actually took the dive into the canal - almost 15 feet - for the Fish-Slapping Dance.
"How To Do It" parodies the long running British children's TV show Blue Peter (1958), in which enthusiastic presenters offer advice and demonstrate various things.