"Dinosaur Ducks" is the eighteenth episode of DuckTales.
The episode starts off with Launchpad chasing a multicolored booby in a mysterious, tropical locale. Once Launchpad catches the booby, he is chased all the way to his plane by a Tyrannosaurus Rex. Launchpad manages to get the booby into the plane and takes off, but a pterodactyl rips off the plane’s wings. Launchpad jumps out of the plane, using the booby to help slow his fall, but the booby flies away afterwards. Tired out, Launchpad crawls (literally) all the way back to Duckburg.
Launchpad eventually crawls his way into Scrooge’s office at the zoo, and tells Scrooge about his failed expedition to bring back a specimen. However, Scrooge is very impressed when Launchpad tells him about how big the tyrannosaurus was, and he declares that Launchpad has discovered a prehistoric Lost World, which is where he plans to go exploring.
At McDuck Manor, Scrooge and Launchpad are loading up a cargo helicopter, when Huey, Dewey and Louie ask to come along. Scrooge won’t let them come because the place is too dangerous, but Huey decides that they can go anyway if they hide in a crate without Scrooge’s knowledge. Webby wants to go with the boys, but when they tell her off, she decides to stowaway on her own.
After taking off, the helicopter eventually reaches the Lost World, where Launchpad runs into the pterodactyl from before. In an attempt to evade the beast, Launchpad screws with the controls, but accidentally sends the copter plunging towards the ground. When Scrooge goes looking for crash helmets, he discovers the boys hiding in their crate. Unable to deal with them at the moment, Scrooge seatbelts them to a seat, which Launchpad mistakenly ejects from the copter. Fortunately, the boys’ seat has a parachute. The copter crash lands, but Scrooge, Launchpad and Webby (who’s hiding in a picnic basket) survive.
The boys land in a plateau; in a large nest, which turns out to belong to the pterodactyl. Despite that, they manage to get away. At this point, a baby duck-billed dinosaur spots them, and decides to follow them in secret. As for Scrooge and Launchpad, in order to reunite with the boys, they are forced to scale a mountain, taking the picnic basket with them. Also, the mother duck-billed dinosaur realizes that she’s lost her baby.
The boys soon discover the baby dinosaur, but their screaming unintentionally scares it off. Louie suggests that they catch the baby for Scrooge’s zoo, but he soon regrets the idea. While Scrooge and Launchpad continue up the mountain, Louie decides that a tiger trap (palm leaves covering a hole) from the Junior Woodchucks Guidebook will catch the dinosaur, provided they make the hole bigger. The trap works, but they end up catching a sabretoothed cat instead.
Scrooge and Launchpad reach the plateau, but they are unknowingly spotted by caveducks. Louie decides to set up a snare trap for the dinosaur, but the boys wind up catching the tyrannosaurus, which chases them and the baby into a dead-end canyon. The boys manage to scare off the tyrannosaurus by pitching rocks to Huey, who bats them at the t-rex with a club. In the meantime, Dewey leads the baby and his brothers into a small cave.
Scrooge and Launchpad stumble onto a tribe of caveducks, who take them away, but leave the picnic basket with Webby still inside of it behind. The caveduck elder then takes Scrooge’s hat and wears it himself. All alone now, Webby decides to go exploring, while the boys set up another trap. As they wait for the baby dinosaur to approach, they spot Webby, just as she spots the baby dinosaur, and attempt to chase her, only to get caught in their own trap. When they catch up with Webby, the boys tell her that the dinosaur belongs in Scrooge’s zoo, but she feels differently.
Webby then leads the boys and the baby dinosaur back to the caveduck tribe, where Scrooge and Launchpad have been tied to a tree. The boys ride into the caveduck village on the baby dinosaur’s back, where Louie lassos the elder with some rope. Huey and Dewey then untie Scrooge and Launchpad, while Louie and the baby dinosaur tie up the elder to the tree. Launchpad uses a stone wheel that two caveducks were rolling to knock aside some pursuing caveducks as if they were bowling pins, while Scrooge retrieves his hat. Webby, who has been left alone again, gets taken in by the caveducks.
Scrooge is not mad at the boys, because they managed to capture the baby dinosaur, which he can use for his zoo. But now, the boys are against the whole idea, and when Louie brings up Webby in conversation, the boys suddenly remember that they’ve forgotten about her, so they all set out to find her, when they go throw the grass they see the tyrannosaurus go roaring but it apparently does not see them, and then head the other way. Eventually, they do find Webby, who is telling the caveducks the stories of Cinderella, Snow White, Sleeping Beauty and The Three Bears as one combined story. Scrooge demands that the caveducks hand back Webby, but is forced to give up his hat to the elder.
The t-rex returns, and chases all the ducks into a cave, but the baby dinosaur is too big to fit. Fortunately, the baby’s mother shows up to ward off the t-rex. Launchpad gets the idea to roll stone wheels at the t-rex, causing it to lose its balance. With the help of the mother dinosaur, it gets knocked off the plateau, and lands in a river.
In the end, Scrooge decides that instead of taking dinosaurs back to Duckburg, he’s better off setting up a safari tour that flies over the Lost World in a helicopter. Launchpad remarks that Scrooge picked a proper tour guide too; a helicopter with an automatic pilot.