The Dark Portal in Outland is significantly larger than the one in Azeroth, what would happen if something big enough to barely fit into Outland one would try to cross into Azeroth? :
Dark Portal | WoWWiki | Fandom
How go to Dark Portal/Hellfire Peninsula, Outland in Patch 8.1 - Alliance and Horde - YouTube
Great moments in PC gaming: Stepping through the Dark Portal in World of Warcraft | PC Gamer
Opening the Dark Portal - Finished Projects - Blender Artists Community