Hello Mineverse! Im gonna teach you on "How to train your Ender Dragon" (Sounds like it could be a good movie) So first of all! You'll need to be quick! You need to run to your Ender Dragon and sit your butt on it! It would destroy your terrain unless you have /gamerule mobGriefing false. You don't have to do this with a dragon you could ride a zombie, a pigment, a Elder Guardian, Even the wither! (The mine cart or boat will explode off his main head unless you have /gamerule mobGriefing false) I enjoy the wither the most because then I could kill all those who appose me >:D. Ok so! Time for the serious stuff.

How to ride a mob on a boat - /summon Boat ~ ~ ~ {Riding:{id:"EnderDragon"}}

Hint: if you wanna do it with a minecart do the same thing but with /summon Minecart

Summoning the wither is weird, instead of keeping it simple with /summon Wither you need to do this - /summon WitherBoss, so its /summon Minecart ~ ~ ~ {Riding:{id:"EnderDragon"}}

I hope this helped!

 

Kewl ;-;

 

Im pretty sure if you use EntityHorse on the enderdragon (Not the wither because the horse would die) you could ride the EnderDragon, I'm too far above the ground to see. Sorry!