The way the characters' mouths distort and distend when they speak has this weird charm to it which probably was a big factor of The Simpsons' success back in the early days. Nothing else on TV looked remotely like it.
According to the commentary they totally can still animate like this today, they just purposely phased out this type of animation by the 3rd or 4th season to make it less distracting or something. I guess there was one director that kept trying to sneak in the backwards mouths a couple times a season just to challenge this.
The animation was originally done by Klaskey-Csupo, they also did Rugrats, Real Monsters, Duckman, Wild Thronberries, Rocket Power, and a couple others I can't think of!
My friends and I used to quote this commercial to each other verbatim during recess in elementary school. Though I thought "die of malnutrition, dude:" was "dye a mound of trition, dude!" whatever the fuck that meant.
No, but when a bunch of bootleg T-Shirts flooded the market featuring Bart with a bong, they decided to ban all Simpsons shirts outright. They also banned the "Big Johnson" shirts, as well.