Jim Henson was determined to use the larger budget of a feature film to push the technological limits and capabilities of puppetry. One of the most difficult feats (and one that appears deceptively easy on-screen) was making Kermit ride a bicycle.
Jim Henson spent an entire day in a 50-gallon steel drum submerged in a pond for the opening scene of Kermit the Frog in the swamp.
When Animal accidentally eats Dr. Bunsen Honeydew's Insta-Grow pills, he memorably balloons through the roof. Jim Henson refused to use a normal puppet on a miniature set to accomplish this effect, so his crew had to construct a gigantic Animal head that measured sixty feet.
Edgar Bergen died shortly after his scene was shot in 1978. It held particular meaning for Jim Henson, who cited, on many occasions, how Bergen and his wooden sidekick, Charlie McCarthy, influenced his interest in puppetry. The end credits include a dedication to Bergen.
In a 2004 interview, John Landis revealed that he was the puppeteer for Grover during the final sequence, as Frank Oz was busy operating Miss Piggy. Landis also noted that Tim Burton was also amongst the many puppeteers in the finale.
Caroll Spinney: Big Bird tells Kermit and Fozzie that he's going to New York City to break into public television, a reference to Sesame Street (1969), the television show that popularized The Muppets.
Frank Oz: Wearing motorcycle gear at the El Sleezo Café. He's the thug who wrestles with Fozzie (one of his main roles).
James Frawley: El Sleezo Cafe waiter. "Maybe he should try Hare Krishna." / "Good grief, it's a running gag."