Many cartoon characters have four digits per hand instead of the five we have, because four fingers are far easier to animate than five and actually look less weird and crowded when the character is holding or manipulating something.
But there would be an unintended consequence of evolving only eight fingers. Any such cartoon civilization would have an octal system of counting, or base eight. This means that the fictional worlds in which they lived would be ruled by completely different numbers than our own.
Important values would be based on powers of eight, so that the octal number ten would represent eight in decimal. 100 would be 8×8, or 64. 1,000 would be 8x8x8, or 512. This would lead to some really bizarre math for any human unfortunate enough to cross over into 2D four-fingered land, and those scores in Space Jam would make no damned sense to Jordan.
6 Unintended Consequences Of Cartoon Character Design
This article is more fascinating when you apply the logic to aliens rather than cartoons. Details are brought up here that I hadn’t even considered in alien based character design.
I recommend this read, from a world-building perspective
A Quiet Respite 