There is a specific error message that Oh Noes detects that should be bypassable. Consider the code: 

noStroke();

var ellipsewidth = 1;
var ellipseheight = 1;

draw = function() {
    for (var y = 0; y <= 400; y+= ellipseheight) {
        for (var x = 0; x <= 400; x+= ellipsewidth) {
            fill(x, x*y, y);
            ellipse(x, y, ellipsewidth, ellipseheight);
        }
    }
};

When run, it should take a while, but Oh Noes stops the program thinking it's a bug. Khan Academy should add a button for specific errors to bypass it, like the loop duration error I got.