That's just the creative mode. That's in 1.8 if you did not know and an op(admin) can switch to mode 0[creative] or mode 1[survival- regular mode you see all of the time] however they please. Plus you can make your own creative world in single player if you did not know.
It quickly went down as soon as I logged into my single player world. I logged in a second time and it quieted down but I still see some red spikes when fps loss happens.
Edit: Sometimes I'm down to 15fps. Dunc I say we put the the 1.7 world for download and start asking people if they want one building they want to save.
Finished my new house(mined and built by hand, though I had to spawn some sheep to get wool since they are nonexistent):
Selling for 650 credits. Everything is handmade and legit with the exception of the spawned sheep(never could find one as if they were all killed and gone!).