Earth, in the 2017 crossover episodes also refered to as Earth 7, is the main planetary setting during the first three seasons of the 2012 TV series, and late-season 4. The planet is home to the human species, but the Kraang Hive Mind intends it to become the new permanent home of the Kraang race. The Kraang even claim to have found the Earth millions of years ago, spending a long time using mutagen to try to manipulate the natural evolution of Earth's life.
In the season 3 finale, Annihilation Earth!, Part 2, the Triceratons use the Heart of Darkness to destroy the Earth in order to permanently destroy the Kraang Hive Mind's operations on the planet. The turtles, April, Casey, and the Fugitoid travel six month back in time and successfully manage to stop the Earth from being destroyed once again.
According to Professor Zayton Honeycutt, Earth's science is 3 000 years behind the galactic standard.