I did so many noobish things, I made a list.
Forgot what torches were
Forgot creepers explode
Learned the hard way that you have to kill the ender dragon to leave the ends
Forgot how to craft a crafting table
Dug down
Made a ceiling of sand
There are so many more noobish things I've done, but these are the most noobish. And finally, the most noobish thing ever...
I've played minecraft since pocket edition came out, and never once did I stop and think that people posted videos on YouTube of themselves playing minecraft. How wrong could I be? XD