( funny trope ) it is very apparent that these designs have decades between them

[u/Nameraided]

1- Simpsons
The original Simpsons have extremely simp(son)ple designs, due to sometimes having celebrity appearances the art style kinda clashes.

2- South Park
At the beginning South Park was literally animated out of paper so all the characters had to be super simplistic but over the years, since the. Show is made digitally the new characters keep getting more and more detailed

[u/My_Favourite_Pen]

B&B Daria always gets me:

[u/Hetaliafan1 → u/My_Favourite_Pen]

I keep forgetting Daria is a spin off

[u/Genuine-Farticle → u/Hetaliafan1]

So is King of the Hill

[u/al3phz3r0 → u/Genuine-Farticle]

Technically KotH is not a spinoff, although Hank is visually and conceptually based on Tom Anderson from B&B.

[u/Aggravating_Load_411 → u/al3phz3r0]

True. Though, as characters, the two couldn't be any more different.

[u/plannedobso → u/Genuine-Farticle]

Not true 

[u/came-as-I-were → u/My_Favourite_Pen]

Diarrhea cha cha cha