I was on a flight once that was de-iced at the gate (of course, this doesn't apply to this flight), and they must have left some ventilation duct open, the smell of the antifreeze used to de-ice the plane entered the cabin and many people started gagging.
I am surprised that this (or worse) doesn't happen more often. I once worked nights at Stapleton International. One morning around 3:00 am, I was told to de-ice some jets. I had never been trained or even seen a de-icer truck before. I had no idea what I was doing and there was nobody there to tell me what to do. I had to get a baggage handler to drive the truck for me while I went up in the bucket. I made the pilots get out and tell me where to spray. I must have cringed for a good hour after each takeoff.
I remain amazed that they would let just anybody hose down a jet just before takeoff. That was just one of several stories and one reason why I hate to fly.