In the first five episodes, Krang tried to conquer Earth with his army of rock soldiers and his mobile fortress the Technodrome. In the last of the five episodes the Turtles trap the Technodrome in Dimension X, along with Krang, Shredder, the Foot soldiers and Bebop and Rocksteady inside it. Since then Shredder and Krang tried in many episodes to get the Technodrome out of Dimension X to finally conquer Earth, but at the end the Turtles always foils their plans. In many episodes, Shredder and Krang tried to conquer Earth by other ways, but these plans are also foiled by the Turtles.
The Technodrome returns to Earth during late-season 2, in Return of the Technodrome, but the turtles send it to the planet's core.
In the season 3 episode The Fifth Turtle, the Earth is one of the celestial bodies in the conjunction where Krang uses Capsidium crystals to re-power the Technodrome. Season 3 also sees the turtles visiting an underground cave, where dinosaurs still live.
Season 3 ends with the Technodrome returning to Earth's surface and Krang trying to send Earth into Dimension X, but instead the Turtles send the Technodrome there.
During seasons 4 and 6, Filo Sopho twice tries to mess with Earth's orbit. In Shredder's Mom, Shredder and Krang try to warm up the Earth in order to force its political leaders to surrender to them. The Vacation in Europe sideseason, which takes place during season 4, had the turtles travelling across European countries, sometimes followed by Shredder and Krang, and sometimes facing other antagonists.
The Technodrome returns to Earth during early-season 5 in My Brother, the Bad Guy but the turtles and Shredder's brother Kazuo Saki, who has travelled all the way from Japan, trap it in the Arctic. In Rock Around the Block it falls to the bottom of the sea.
Season 7 ends with the Technodrome, in Shredder Triumphant!, returning to Earth's surface before the turtles send it empty to Dimension X, trapping Shredder, Krang, Bebop and Rocksteady on Earth.
During the last two seasons, when Shredder and Krang were trapped in Dimension X for good, extraterrestrial warlord Lord Dregg tried to conquer Earth by manipulating the people, letting them believe that he is an hero who came to save them. The Turtles unmasked him and trapped him in Dimension X.
However, Shredder, Krang and Dregg were not the only ones, many villains tried to conquer Earth or parts of it, but at the end the turtles stopped them.
- Brazil (Star of Brazil)
- Denmark (it's embassy to the USA)
- Sweden (Sven Svensson's native country)