It is a Zombie riding a Wither Skeleton Skull.
Have Fun!
Note: Minify the command to avoid issues :)
Zombie Calvary Soldier
Vanilla Turf Wars Gun Salesman
Drugdealer v1.0
Red Order Form
Pet ENDER DRAGON!!!!!
Wither Storm Boss in ONE COMMAND
HEROBRINE COMMAND
HEROBRINE BOSS BATTLE (See YouTube for details)