When Sirius was a colt and lived with his mothers in Canterlot, he didn’t have many friends. Most foals in Canterlot were stuck up and too brown nosy for Sirius to deal with. His only true friend was Toxic Love, the ever elusive prankster that broke into the castle. Sirius knew his mother was an enemy of Equestria but felt no ill will toward Toxic.
 
The two quickly became friends and were often found playing together. Sirius thought he was a super smart colt, be able to be friends with a changeling without his mothers knowing but he was only half right. While Twilight was unable to tell that the colt her son played with was a changeling, Celestia was more than aware. She welcomed their friendship, hoping it would lead to a better relationship with the enemy queen.
 

 

 
 
Too bad this lovely friendship was doomed to fall apart sometime after Celestia’s disappearance.