Right when Ira is talking about how the aliens weakness is Selenium, Deke, The failing student, announces that Selenium is the active ingredient in Head and Shoulders brand shampoo. Then Ira tells Deke he gets an A on his test.

However...

Selenium is NOT the active ingredient in H&S, it is Zinc Pyrithone.

Also, Selenium isn't in the inactive ingrediants either. Selenium isnt ANYWHERE on the whole bottle of any kind of H&S.

Deke, you get an F.