The Simpsons (1989)

S12E9 HOMЯ

In an effort to recover his family's lost savings from a poor investment, Homer takes part in a research study as a human test subject. During this experience, he uncovers the surprising reason behind his low intelligence: a crayon that has been stuck in his brain since childhood. Determined to boost his IQ, he opts for its removal, only to find that higher intelligence doesn’t automatically bring him happiness.