Simpsons Treehouse Of Horror #19

"After being sentenced to serve detention in old library in the subterranean bowels at Springfield Elementary, Bart discovers The Book of the Dead and accidentally unleashes the Cthulhu on an unsuspecting Springfield. Then, Lunchlady Doris is finally fired for serving subhuman grade cuisine and replaced by the best the school food service industry has to offer. Soon the students are healthier and smarter than ever before, which can only lead to one thing - world domination! (And you thought we meant better state test scores.)"