Phil Deedle and Stew Deedle are two fraternal twin brothers who are complete surf bums living in Hawaii off of their wealthy father. After the two decide to skip out on school to go on a special surfing expedition with friends for their birthday, the twins are expelled from their high school for truancy. Their father Elton Deedle has become tired of their insolence and lazy lifestyle and thus decides to ship them to a boot camp to straighten them out. The boys are horrified that they’re going to have to fly state-side in order for this to happen, as the camp is located in Yellowstone National Park in Wyoming. The boys arrive in Wyoming ill prepared for the far-cooler weather, disembarking from their plane dressed in shorts, flip-flops and hula shirts. They attract the attention of a small crowd when they summon a remote controlled crate containing a mini-bar that they use to create hula drinks. Afterwards they leave the terminal, noticing a gruff looking mountain man whom they make fun of, to their shock the man reveals a sign with their last names written on it, indicating he’s their ride. Major Flowers is already disgusted with their behavior, on the drive back to Yellowstone from the airport, Flowers reveals that his once successful camp was shut down by the children’s parents and their lawyers but the camp wasn’t necessary anymore because he intended for the Deedles to undergo survival training. Flowers becomes distracted in describing his plan and fails to pay attention to the road, eventually driving over the edge of a hillside and crashing into a river. Thinking he had killed the Deedles, he runs off thinking he’ll hide from the authorities. The Deedles awaken from their crash and find some women’s clothing that had caught onto Flower’s truck before it crashed, since it was their only option for dry clothes they opted to wear them. After, they begin to hike towards the parks main entrance, they find some of their gear and decide to land-luge down a long hill with their hula crate remotely in tow. They bypass a long line of traffic awaiting entry into Yellowstone but unable to slow down or gain enough control of their boards they crash into the park’s sign and are then collided into by the hula machine—cracking their helmets off. When the Park Rangers arrived, the only identity the boys had on them were the names “Mel” written on Phil’s sweatshirt tag and “Mo” written on Stew’s. After the incident the boys are carted off to the Ranger medical center and nursed back to health and decide to assume the false identities as it appears to be a one-way ticket to success and approval of their father.
The boys find it difficult to live in their new identities, as the park rangers have already learned that the “real” Mel and Mo are vegetarians, thus the boys are forced to become such as well in order to maintain their cover. Because of their dimwitted surfer nature, the boys do not click well with the commanding park ranger, Captain Pine, although Phil falls for his stepdaughter Lt. Jesse Ryan whom the Captain is very protective of. This leads to a series of accidents all of which the Deedles are to blame for and land them in disfavor with Captain Pine. Through their trials, the Deedles inadvertently discover that an ex-park ranger named Slater feels he’s been betrayed by the park, the Rangers and mainly Captain Pine and so he has created a secret bunker underground near Old Faithful and has devised a plan to divert Old Faithful’s waterflow into a new geyser he’s created on his own land which he is christened “New Faithful”. Unable to win any support for investigation from their fellow rangers, the Deedles take matters into their own hands and attempt to thwart Slater’s plan. However, the real Mel and Mo arrive at the Ranger’s base at a very untimely moment to reveal that Phil and Stew are not who they say they are. Pine, Jesse and the other rangers are disgusted with their dishonesty and banish them from Yellowstone. As the Deedles are walking down the highway attempting to hitch-hike, the big picture dawns on Phil and they devise a plan to get back into Yellowstone in order to stop Slater once-and-for-all. They rig a grappling hook into a grate in the roadway, and as an unsuspecting car passes it would catch the undercarriage and tow the Deedles (whom are wearing parachutes), essentially a land version of parasailing. From a few hundred feet up in the air, they both notice a familiar stench and discover the person towing them is none other than Major Flowers—whom becomes distracted by his stowaways and subsequently drives over a cliff (again) landing himself in a river. The boys parachute to the entrance for Slaters underground tunnel network and go underground, where they locate and subdue Slater’s two cronies Mr. Crabbe and Mr. Nemo. They devise a plan to re-divert the water from New Faithful back to Old Faithful, and to escape by donning heat-resistance suits and escaping through the plumbing and through Old Faithful’s spout. The plan succeeds, Slater is exposed and the Deedles become heroes for saving Old Faithful. In a fortunate turn of events, the force of the explosion of water was so great it created a small lake which naturally created waves large enough to surf on, and the boys were able to create a park out of it. Earning the respect of their father for their success, from Captain Pine for their help in saving Yellowstone, and for Phil the love of Jesse.
Steve Van Wormer as Stew Deedle (Stuart Michael James Deedle Esquire)
Paul Walker as Phil Deedle (Phillip Andrew Preston Deedle III)
A.J. Langer as Lt. Jesse Ryan
John Ashton as Capt. Douglas Pine
Dennis Hopper as Frank Slater
Eric Braeden as Elton Deedle
Richard Lineback as Crabbe
Robert Englund as Nemo
M. C. Gainey as Major Flower
Ana Gasteyer as Mel
Megan Cavanagh as Mo
Hattie Winston as Jo-Claire
The film also features cameos from former Oingo Boingo members Steve Bartek, Johnny "Vatos" Hernandez, Carl Graves, and Sam "Sluggo" Phipps as the band at the luau.
"Meet the Deedles' soundtrack"
The original music for the film was composed by former Oingo Boingo member Steve Bartek. Most of the songs featured on the soundtrack were from third-wave ska bands, as the genre was at the peak of its popularity at the time of the film's release.
"Wrong Thing Right Then" - The Mighty Mighty Bosstones
"Lady Luck" - Dance Hall Crashers
"Seems Like Yesterday" - Goldfinger
"Dr. Bones" - Cherry Poppin' Daddies
"I Can't Wait" - Hepcat
"Psycho Gremmie" - Gary Hoey
"For You" - Save Ferris
"Go Where You Go" - Geggy Tah
"Failing and Leaving" - Radish
"American Girls" - Homie
"Hawaii Five-O" - Perfect Thyroid
"Who Are Those Guys?" - Steve Bartek