“Journey to the Center of the Earth! [Chapter 1”
Simon and Cad build an Earth Sub to drill through the center of the earth. They plan on going to Australia to rob a bank. They are captured before getting half-way there by the Glops, bugs with 4 arms.
“The Lost City [Chapter 2”
Underdog saves Simon and Cad from the Glops, and solves an ages old dispute between the Glops and the Gleeps. Meanwhile, Simon and Cad get away and continue drilling through the earth.
“Earth's Core [Chapter 3”
Simon and Cad arrive at the earth's core, where they find a band playing (because "Music is what makes the world go 'round, man!"). Underdog, again, saves Simon and Cad and then grabs onto their Earth Sub for the rest of the journey.
“The Mud Creeps [Chapter 4”
Simon, Cad and Underdog are captured by mud monsters, but Underdog defeats them by mushing them all together. He follows Simon and Cad to their destination, but somehow they got off-course and end up in a Chinese restaurant instead of an Australian bank. They order lunch.
