Reminds me of an incident from back when all this single engine taxi nonsense started. I was a 767 F/O in BOS, it was winter, the ramp was covered with fresh snow/ice. We pushed back, turning about 90 degrees away from the gate, so the jetway is now out my right window. I'm starting the left engine, it's running and the Capt. is getting the wave off from the tug crew.

I say, "You want the right engine too?" as I'm reaching up for the start selector.

He said, "Naw...we'll be fine on one." as he pushed up the power on the left engine.

Well the airplane spun hard to the right, and now we are looking right at the tug crew who's eyes are wide open, mouths too...like this:

I look at the Capt. and calmly I say,

"OK.... do you want me to start the right one now?"