yesterday as we were about to push back on our SEA-DFW flight on a 738 the pilot came on to tell us the wings needed to be rinsed off (??). Sure enough a few minutes later a de-icing truck with scissor lift pulls up and starts to spray what appears to be water. FWIW it was in the mid 50's outside.

Anyone had this happen before? Did some Canadian honkers crap on his wing?