While attempting to log into a single player world I had previously put under large server-side load, I encountered an odd linking of buttons. I was trying to replicate bug MC-56845 in a test world, and was expecting the client to crash due to extreme server load. After "successfully" loading the world, I let it sit for a while. After about a minute, a "server closed" dialog popped up, with a main menu button.

What I expected to happen:

The screen to return me to the main menu, or at least the single player world select.

What actually happened:

The screen took me to the multiplayer server select menu.

I was able to repeat this a couple of times while the world's server was still under load, with both doing nothing on login and attempting commands/moving. After a while longer, the expected crash did occur. I've added that report, however I don't see it as necessarily related to this bug.

Obviously Mojang didn't expect someone to crash the single player server in such a way, but I thought it worth mentioning. More details available in aforementioned bug, however I can X-post if it will help.