The Mutant Apocalypse in Equestria
 
Littlepip since childhood wanted to be a ninja like the turtles, Twilight then trained her when she was a child, and Littlepip was already learning fast, but one day, the Mutagen Bomb exploded in Equestria, and Littlepip and other ponies hid in the stable 2. 10 years later, Littlepip left the stable when her best friend Velvet Remedy escape, after Littlepip left, she didn’t want to go back, because now she was free (even in a Mutant Apocalypse desert) after that little journey, she find Velvet and her other best friends, Calamity and Blackjack, then all went on a wasteland journey, faced many enemies, and finally met the turtles, and Littlepip was reunited with his teacher and friend princess, Twilight Sparkle.  
From TMNT Mutant Apocalypse and Fallout Equestria
 
Base by Pastel-Pocky  
https://www.deviantart.com/pastel-pocky/art/Proud-of-you-MLP-Base-816750089