OMG I looked above the unlit oil can on the barrel stage and thought there was dust on my monitor. But there are actually two pixels that make up the hitbox that makes you die when you jump there.
And I noticed something that I cannot explain. These two pixels are also seen at the top left of the rivets stage, a little between the umbrella and the top left rivet. I do not know why it is there. I guess that that is the same sprite that is also used above the oil can. But why is it there? And then when playing the pies board I see those pixels again, about the same spot, but they move left and right just like DK does. It looks like that that sprite (originally a blank one) is somehow drawn as part of DK? But why?