You were chilling in the nether, doing random shit. Trading with pigmen, crossing lava, and getting blaze rods, via invading nether fortress's, you decide to (for some reason) go to the top of the nether!... Why?, for fun of course. And after, somehow you got past the bedrock, and now you're at the top!. Well, there isn't much, considering it's a flat bedroom plane with a red sky... Oh hey, is that a giant ghast?

..wait a minute, that's the ghast titan!, wow.