Yulon on Tumblr found a really nice easter egg in Warlords of Draenor. The first followers — NPCs we can send out on missions for some extra loot — we can hire for our Garrisons both on the Alliance and the Horde side actually match characters from World of Wacraft's very first cinematic trailer that came out a decade ago.
Two characters, to be exact: the night elf Qiana Moonshadow (see the pic on top) and the Tauren dude Olin Umberhide. Unlike other characters in various WoW cinematics, these guys weren't really revealed, looking just like generic adventurers representing in-game classes.
Everything matches, even their armour, and even if it's just a reference and they're not the same characters, it's still pretty cool. One of those "mind = blown" moments.