New Earth Prime is the name of the version of Earth created by the merging of the DC universe and the world of the Ninja Turtles. Krang produced this world with the Crisis Tower, as part of the attempted merging of the two multiverses.
Many individuals in this compound universe were merged with another, such as the combination of Shredder and Joker into the Laughing Man. Others, such as James Gordon and Casey Jones, were altered so that Batman and the Ninja Turtles would have fewer allies.
New Earth Prime was also the destination for the progenitor Raphael, who was seeking the Turtles from Krang's own dimension.