a). Anagrams are not funny.
b). Puns are not funny.
c). Cleverness is not, in and of itself, funny.
d). Guest stars that play themselves are, generally speaking, not funny.
e). Homer singing is not funny.
f). Long series of product names altered slightly from their originals (e.g. Sketch-n-Etch, Ravenous Ravenous Rhinos, Herschel's Smootches) are, pursuant to b), not funny.
g). Homer suffering brain damage is no longer funny.
h). Bart hinting at deep-seated emotional problems underpinning his behavior is still hilarious.