Ms. Ellen

Ms. Ellen was a substitute teacher in episode 111, "Tom's Rhinoplasty".

Sexual Orientation
She caught the attention of Stan Marsh who threw up every time he saw her. This made Wendy Testaberger jealous and she organized a plot to get rid of her from the school. When Stan tells her how he feels, she explains to him that she is a lesbian. The four boys then proceeded to eat a box and munch carpet, literal examples of lesbian sex.

Name Origin
Her name is an obviouse reference to lesbian actress Ellen DeGeneres.