What I expected to happen was...:
I thought that I would play a normal singleplayer world

What actually happened was...:
I could see the chat of the multiplayer world, but when i tried to say things, the people in the multiplayer side seemed to not be able to see my messages.
The day/night cycle was going really fast, and kept switching between something like day 50,000 and day 351.
No new hostile mobs were spawning because the day and nights kept switching really fast, so i guess that would make sense.

Steps to Reproduce:
Go to into a multiplayer world with very bad wifi.
Leave while it still says "connecting to server"
Then go to a singleplayer world.

In the screenshot, you could see the chat being as if it was in a multiplayer world, but the social interactions feature said that it was a singleplayer one.

Sorry for the bad descriptions, haha.