You can summon ghastling using this command (Image via Sportskeeda Gaming || Mojang Studios) Once you have allowed commands in a world, simply type the summon command to get a ghastling to spawn.

In Minecraft Java Edition, there is a small chance that certain hostile mobs can spawn with armor parts or any item in their hands.

If you'd like to check out the original Herobrine world for yourself, you'll need to use Minecraft Java Edition with "Historical versions" enabled in the launcher.