Yes, that's right!
Two episodes I've seen have had pics of brains in jars:
Duffless - Very opening scene, when Bart is dreaming of his science fair result. One of the other classmates has a brain in a jar for his/her science fair project.
Treehouse of Horror VIII - Fly Vs Fly segment - When Homer is at Frinky's yard sale, one of his objects for sale is a brain in a jar.
Does anyone have caps of either of these?
TIA
Jase.