Underdog breaks out of the phone booth, and hears the cries for help again. Underdog flies to the lady, who tells him that her little boy has been accidentally locked in a bank vault. With only this information, Underdog flies off toward the bank. He reaches a bank, crashes in, much to the shock of the occupants, and then proceeds to rip open the giant door to the vault. The bank president blows up at Underdog, saying that he's got the wrong bank! So, Underdog flies to the correct bank, and attempts to rescue the boy. But at first, nothing he tries works. He crashes through the vault door, only to crash through the whole building and the one next door as well. He tries using his X-ray vision to locate the boy, but instead, starts a fire! All the people in the bank are in a panic now! Underdog uses his atomic breath to blow out the fire, and in the process, blows virtually the whole building away! But at least the mother's little boy is found all safe and sound.

An army of giant robots take over the city and capture Polly. Underdog foils the monsters by using his high-pitched voice to destroy the robots' electronic brains. The robots aren't the only thing destroyed, but so is all of the city's glassware.

Simon, a mad scientist, creates a camera. This is not some ordinary camera however. When he takes someone's picture, the freezes them in the photograph!

Simon Bar Sinister creates a new super weapon: the Go-Snow Gun. The gun freezes people, turning them into snow people. Simon and his Henchman Cad take over the First National Bank, holding the bank President, his staff and customers prisoner.

Underdog is having an average day. He foils a bank robbery, rescued Sweet Polly and made himself useful across the world. Meanwhile, a million, million miles away on the planet Zot, King Klobber is upset. It seams that his daughter the princess wants to get married and can't find anyone suitable.

The story of Zot continues with King Klobber searching the galaxy and then the universe for the strongest warrior. They discover Underdog on an insignificant planet named Earth. King Klobber sends a fleet of spaceships to capture underdog and return him to the planet Zot.

As the story of Zot continues King Klobber of Zot sends a spaceship to capture Sweet Polly Purebred. He holds Polly under "The Great Zot", a 10 ton weight. When Underdog arrives to save Polly he agrees to marry the princess if Polly is returned safely to Earth.

The story of Zot concludes, as Underdog and the princess are about to be married. Just at that moment the evil two-headed dragon attacks the city. Underdog defeats the dragon and saves the city. King Klobber grants underdog a favor and he asks to be allowed to return to Earth without marrying his daughter. The King agrees and the princess decides she was in love with the Prime minister of Zot all along and all are happy.

Riff-Raff is no longer Public Enemy No. 1, so he comes up with the ultimate plan: robbing a trainload of gold by distracting Underdog from his duties of protecting the gold on the train.

Riff-Raff's plan goes into action: they kidnap Sweet Polly Purebred, tie her up and put her in a balloon, and set up a bunch of other balloons with record players inside them playing records of Sweet Polly shouting "HELP! HELP!" Once the plan is under way, Riff-Raff's gang heads over to the train station and hold up the stationmaster, and Underdog leaves his post and heads over to the balloons, only to be confused by the record players.

Underdog is still confused and frustrated trying to find Sweet Polly among all the balloons, so far only coming across the record players Riff Raff's gang implanted in the balloons. But then Sweet Polly's balloon springs a leak and is plummeting towards earth toward a hungry alligator. Underdog then finds the real Polly in trouble and saves her from danger. Meanwhile Riff-Raff and his gang take over a railroad station, planning to throw the switch so the gold train Underdog was guarding will collide with another train.

The train full of gold is about to crash into another train, with Riff-Raff's plan going just as he expected. However, Underdog has just rescued Sweet Polly and manages to make it in time, stopping the two trains before a major derailment occurs. Underdog then chases Riff-Raff throughout the station winds up catching Riff-Raff, and all is well once again.

Sweet Polly Squeeze boards a ship to travel to a south sea island to investigate the world's biggest monster "Fearo the Ferocious".

"Fearo the Ferocious" captures Captain Coward. It's Underdog to the rescue.

Simon Bar-Sinister invents "shrinking water" which shrinks anything sprayed with it to the size of his thumb. He kidnaps Sweet Polly to lure Underdog into a trap.

After being shrunk by Simon Bar-Sinister Underdog and Polly are imprisoned in a birdcage in Simon's lair. They escape into the garden and hide in a rat hole where they are attacked by the rats living there.

The shrunken Underdog and Polly make their way through Simon's garden to try and stop Simon's plans, facing rats and eagle attacks. Meanwhile Simon sets up his cloud making machine to create a cloud of shrinking water over the city.

Simon shrinks the inhabitants of the city, as well as his henchman so he can be the tallest man in the world and then lies down for a rest. While Simon is asleep Underdog uses a double dose of shrinking water on Simon to make him smaller than everybody else and then tickles the shrinking cure out of him.

Underdog's double, an evil criminal, plots to steal a priceless diamond after he escapes from prison.