The Jungle Cruise boat ride that debuted in 1955 at Disneyland has seen the script used by the skippers change and evolve over the decades to introduce jokes about angry hippos, leaping tigers and the backside of water as the attraction has been updated and refreshed.

Jungle Cruise skippers memorize hundreds of “corny dad jokes” for use in the Disneyland attraction spiel, according to “The Happiest Story on Earth” special on ABC’s “20/20” newsmagazine TV show.

“When we hand our brand new skippers that spiel, it can be intimidating because there are 600 jokes,” Disneyland Jungle Cruise Skipper Kristi Newsander said on “20/20.”

The Jungle Cruise ride that debuted on July 17, 1955 with the grand opening of the Anaheim theme park was inspired by Walt Disney’s True-Life Adventures nature documentary films and “The African Queen” adventure film from 1951.

The opening day attraction that simulated a 10,000-mile journey along the Irrawaddy, Mekong, Nile and Congo rivers had a very dry, factual narration that was more educational than entertaining.

The skippers added jokes to the official script in the 1960s after Walt Disney asked animator Marc Davis to sketch some new scenes that would introduce more drama and humor to the ride.

“Walt heard that skippers were starting to put jokes in,” Newsander said on “20/20.” “He said, ‘Put me on a boat that does the jokes’ and he loved it.”

The Jungle Cruise script has been updated throughout the years as Walt Disney Imagineering introduced seven new scenes in 1976 and rerouted the river in 1995 to add the Indiana Jones Adventure next door.

At least eight Jungle Cruise skippers who refused to stick to the script were fired in 1997 after a crackdown by Disneyland on unauthorized jokes, according to the Los Angeles Times.

Imagineering gave the attraction a temporary holiday makeover in 2013 and stripped the ride of racist tropes while adding new scenes in 2021 as Disney launched a new film franchise based on the Disneyland attraction starring Dwayne “The Rock” Johnson as a riverboat skipper and Emily Blunt as an intrepid explorer.