Adult Spike
sorry for the messiness, but i was feelin too lazy for lineart. so it's just a colored sketch.

but anyway, this is my headcanon for what spike will look like as an adult. He can still stand on his back legs if he wants to, but he usually walks on all fours since he can and it makes him feel like he fits in with the ponies better that way. He still has no wings, he is still chubby-ish, and he got a different scale pattern. He of course got much bigger, with a longer nose and different proportions and stuff, but other than that, he is mostly the same.

Also, I threw in a Rarity for size comparison.