They have a thin candy shell.
4 seconds sound clip from the Tommy Boy (1995) movie soundboard.
You can hear this line at 00:07:35 in the Blu-ray version of the movie.
Quote context
[...]
- Hey, what's new with the old gang from high school?
- I don't know. I didn't really like the old gang from high school.
- Hey, the muffler plant's gone too! Yup.
- Man...
- Oh, that sounds good. Melted chocolate inside the dash. That really ups the resale value.
- I think you're gonna be OK here.
- They have a thin candy shell.
- I'm surprised you didn't know that.
- I think your brain has a thick candy shell.
- Your brain has the shell on it.
[...]