First, what's the point of copying someone else's artwork for your assignment. It's plagerism and, at least, cheating. If your teacher has ever even glanced at the original, you'd probably fail the project, if not your class!
Second, you know darn well that the style of a cartoon character is not "realism." If the subject is to be a couple of human beings, then they should look like human beings as close as the artist can manage.
If you still think this idea is worth pursuing, then I suggest you find a couple of friends and set them up in a pose that suggests the layout of, either, the Bevis and Butthead illustration, or, even better, the original Michaelangelo fresco of his Genesis scene. Then, it wouldn't be a copy, but a parody. (which the Bevis and Butthead illustration was) In your case, a parody of a parody if you want to stick to the Bevis and Butthead theme.
But the point of your assignment is that the illustration captures the realistic depiction of your models.