Single Point of Failure - S1-E2
Revealing mistake: Walter accesses code on the sick girl's laptop to trace the source of the virus - aside from the fact that the code comes straight up a fraction of a second after his hands even touch the keyboard, the code displayed in the black window is for a set of traffic lights, with lines like "Walk/Dont_Walk" and "Green_Arrow/Yellow_Slow." (00:08:10)
Single Point of Failure - S1-E2
Character mistake: In the letter informing him of his sister's condition it says "Nor have I scene" instead of "seen". I would not expect a medical professional to make that sort of error. (00:02:20)
Answer: A propeller sucks in from one side and pushes away from the other side.