In a survival world, I wanted to get into the Nether. So, I went through my Nether Portal (duh.) However, instead of waiting, the game sent me into the Nether immediately. And it took a really, really, REALLY long time to load. (That might just be me, though).
To Replicate:
1. Build a Nether Portal
2. Go through it.
Intended when you are in creative mode.