So Toxic might be the only one so far to not have changed as I drew his foalhood. How nice.
* Toxic loves himself and shows himself off at every opportunity. The drones adore him, since he is their future king, and act as his backup. If he's showing himself off, there are usually a few drones creating a spotlight for him. If by himself, Toxic will just make himself super noticeable. The only time he doesn't show off is when he's playing pranks, for obvious reasons.
* Toxic absolutely adores Sirius, even though the oblivious prince just thinks hes affectionate. I like to think that Changelings mark their mates with a special pheromone that only other Changelings (a select few creatures) can sense. Toxic is constantly marking Sirius, though he isn't consciously aware of it. He just likes the fact that his smooches make his darling Veil smell like him.
* Toxic has very few interactions with adult ponies, though he has been caught by a few. His solution is to scare the piss out of them with something he can do, usually grabbing them with his tentacle like tails. This time however, he was honestly pleased by the stallions complement and wanted to show his appreciation with a smile. Unfortunately, his fangs tend to scare ponies.
* Toxic loves and respects his mother but there are a few things he stands against her on. One of the big ones is her treatment of Albino Changelings or pale-shells. They aren't born often but when they are, Chrysalis usually dumps them somewhere to die. She doesn't hate them but this has been the way the Changeling Queens have handled pale-shells for centuries. Toxic doesn't like this practice, chastising his mother for her heartless abandonment of her children just because they are pale shelled.
* Toxic, despite his love for the Pale Shells, learns a harsh lesson. Love can't save everyone. His mother tries to tell him that the reason she leaves them to die (or kills them herself) is because they die very soon after being born. No one knows why but her actions, she claims, is an act of mercy. Toxic refuses to listen and tries to take care of them himself. He wakes up one morning to find all the pale shells dead and no clue how to handle it. Even when his mother tries to comfort him, he snaps at her, running away for a few days. He spends those days with Sirius, crying into the colts coat until he falls asleep. He never told Sirius why he was crying and Sirius never asked.
Note: Toxic's mane will change depending on how he feels. When he gets angry, his mane vibrates before exploding into a spiky mess. His mane can legit cut ponies when it gets like that. It's not as flexible and soft at those times but its much harder to cut through.