As dectected in the fuel supply by W.C. Fields. The term "Ubangi" denotes a black person. Taken altogether, the somewhat-famous Fields quote simply indicates something out of place or awry, some evil intent. Fields wrote in the 20's and 30's, so those people in positions of social power then didn't necessarily consider this offensive.
"I detect a Ubangi in the fuel supply." -W.C. Fields