“Matthew Abraham “Matt” Groening is an American cartoonist, writer, producer, animator, and voice actor.
He is the creator of the comic strip Life in Hell (1977–2012) and the television series The Simpsons (1989–present), Futurama (1999–2003, 2008–2013), and the upcoming Disenchantment (2018).” (Wikipedia)
Bart called them out on their dumb, cliched lines. And how stupid they ultimately were.
Then you realize these three depraved kids simply can’t understand that a nice normal loving mom like Marge does buy pyjamas for her 10 year old son. Obviously she does. It’s why they’re so stunned. They have no concept of that.
(We were told more than once Nelson, at least, was neglected by his mother.)
Bart is incredibly lucky compared to those three.
One of the deepest, darkest moments of the show, IMO.