Get you best paper, cut a circle and fold it so that the circumference falls on a fixed point inside. Repeat, using random folds. Now see the creases. This is how you paper-fold an ellipse.
i guess you could say pythagoras had an irrational fear
From Shouldn’t We Teach GEOMETRY?, Branko Grunbaum, The Two-Year College Mathematics Journal, Vol. 12, No. 4 (Sep., 1981), pp. 232-238
I will read anything by Grunbaum.