"Ug! It's an ug-cellent Ice Age adventure set to Calypso as Cave People Uniqua, Pablo and Tyrone invent their way to Tasha and Austin's cave for something called 'a party.'"
Tasha and Austin are seen in the backyard wearing white rock necklaces. They introduce themselves to the viewer as the Mountain Cave People. Tasha and Austin tell the viewer a word known as "ugh", which can mean anything they want it to mean. They start to sing the song "Three Cheers for Ugh!" Then, the two Cave People walk off into the backyard.
Uniqua, Pablo, and Tyrone introduce themselves as the Valley Cave People. They walk over to a tree and see a note. The note is from the Mountain Cave People, and it is an invitation to howl at the moon when it is at its highest peak. The three accept. The backyard transforms into a prehistoric, icy land. The camera moves away from Uniqua, Pablo, and Tyrone, who are now slowly walking to the mountains, and to the Mountain Cave People. Tasha and Austin are living in a large cave on a mountain. They are waiting for the Valley Cave People.
Since many things have not been invented, cave people can invent things a lot. Austin grabs two sticks and a large base and invents "the drum". Tasha likes the idea and makes one too. They start to play the drums while singing "Drumming Song". Meanwhile, the Valley Cave People are questing through the ice age to the mountain. They come across a frozen pond.
The three need to find a way to get across the ice-covered body of water. Pablo gives himself, Tyrone, and Uniqua a pair of inventions that he calls "ice skates". They sing "Skate Ahead" as they use the skates to get across. Now, the three notice the moon - almost at its highest peak. They come across a hill, leading to the Mountain Cave People. Uniqua shows them an invention she has created called "the stairs". After a lot of walking up the stairs, Uniqua states that next time, she will invent the elevator. They arrive at the top of the hill.
The trio all realize that they need something to get down the hill faster. They invent the "sled" so they can race down the snow faster than walking. Meanwhile, at the top of the mountain, the Mountain Cave People are thinking of a way to let the Valley Cave People know where to go so they don't get lost. They invent the "arrow", like a sign, which will help the guests know where to go. They start setting up the arrows.
Uniqua, Tyrone, and Pablo have already gotten to a large slope area, the trail leading to the Mountain Cave People. They see the arrows that the Mountain Cave People have invented and walk where the inventions point. They arrive at the Mountain Cave People. And the moon is just at its highest peak. All five howl at the moon together.
Next, Tasha and Austin show the guests another invention: the Hokey Pokey. They sing the song "The Hokey Pokey" while dancing to the music. Pablo's stomach growls. Tyrone asks if the sound was a cave lion. He tells him that it was just his stomach, and invites his friends over to his house for cinnamon toast. The ice age turns back into the backyard, and the Backyardigans sing the end song. Everyone rushes into Pablo's house for a snack. Austin opens the door and he exclaims, "Ugh!"