jk i would never make you imagine the dragons they're right here
have some headcanons on em

Female dragons have horns, males don't. I'm thinking they can channel dragon magic through them?
Garble, despite his big guy attitude towards Spike, is a pretty weak and small dragon. Male dragons love to fight and spar and while Garble puts on a big show he's really…not great at it, and he doesn't exactly enjoy getting beat up by the other dragons. He's more of an artist than a fighter, but good luck getting him to admit that, especially when he's being challenged by a dragon twice his size. He might not be a great fighter but he AIN'T NO COWARD. He'd probably be smarter if half his brain cells hadn't been knocked out by 12.
Garble hit puberty pretty early and thus was kicked out of his house at a young age. Not every dragon family follows the strict traditionalism of kicking a hatchling out when they molt, and Garble's family specifically did give him the choice to stay…but of course his macho big guy attitude wouldn't allow him to accept their offer. Ouch.
Dragons lose and regrow their teeth, like sharks
The dragon eyes are weirdly inconsistent in the show (some of them have "pony" eyes with white sclera and colored irises, and some have more "animal/monster" eyes with colored sclera and black pupil eyes) sooo I'm gonna make up my own design "rules" for them (and maybe sometimes keep the show portrayal if I think it looks nice, like Garble). I like to think that dragons and bat ponies have some common ancestry so I'll give them the same inverted dark sclera/lighter iris with a slit iris. Spike gets to keep his pony eyes on account of some magic shit that happened when Twi hatched his egg also because I made up these rules after I drew him.
i like the dragons hehe. I even like Garble even if he's kinda unpopular. I ship him with Spike, I know Spike's age is kinda weird and some people see Garble as an adult but I always saw him as like a really big/mature looking teen, one who might even be mistaken for an adult. Whereas with Spike is a very babyfaced teen dragon up until he's older…..I've talked about my headcanon on Spike a little before, mostly about what kinda dragon he is. But one thing I've never mentioned is that fact I find his relationship with Twilight a LITTLE messed up. Not by any fault of Twi, who seems like she was about 12 when Spike was thrust upon her, but the entire relationship in general. Is Spike supposed to be her pet, assistant, son, or little brother? The show seems to want him to be all four at different points but those are VERY different roles…Spike is a whole sentient being. What kinda school entrance exam is hatching a whole baby and then…having to take care of it? What the hell Celestia. Where did you get that egg. Does Spike have real parents? Does he think of Twilight and her family as his own? It seems like towards the end the show seems to answer that question with "yes", but that honestly makes his treatment in the early seasons seem even worse in a way?

Basically what I'm trying to say: Spike's got baggage. I like to imagine during his rebellious teen years he starts to embrace his "dragon" side more, maybe even being a little resentful of the ponies who raised him for a while. He wears a spiked collar with an S for Spike (NOT Sparkle) because hey, he's been raised like a pet so he might as well look like one. The whole thing breaks Twilight's heart in a billion different ways and results in her trying to fix their relationship. Eventually, the two do make amends, Spike realizing Twilight isn't really the one to blame. He even forgives Twilight's parents with time, realizing their lack of experience with dragons may have had something to do with the neglect he suffered. One thing that helps him along is his relationship with Garble who has…different family issues. The two end up settling in a small cave on the outskirts of Ponyville. It's the home-iest cave you've ever seen, Twilight was pretty surprised to find not only furniture, but also plumbing and electricity when she visited. How the hell did you guys rig a cave to have modern plumbing.

also. Does anyone else think about how they made Spike's little cheek flaps translucent in the MLP movie. I think about that a LOT. IDK why. it kinda makes him look like a frog tho. thoughts?
also yes I know I drew his little green flappy thing inconsistently…i was still working out his design also dragons aren't real so who knows. maybe they can change when they molt.