why do all cartoon characters always have 3 fingers , even the animals do too?

Not All Of Them ..

It depends on the cartoon, but generally those with characters of anthropomorphic animals tend to have hands with three fingers and thumb instead of four fingers like humans. Overall it's easier to animate, because hands have a wide variety of positions.

I heard (not sure how true, but sounds feasible) that in the early days you couldn't get as much detail as today, so trying to fit all 4 fingers and a thumb on a hand resulted in it looking too big.

And then, even though today techniques have improved, some folks carry it on like a tradition.

(come to think of it, it might even have been on a Simpsons or Futurama commentary)

What cartoon have you been watching because i haven't seen a cartoon character with three fingers yea probably an animal because maybe that how the animal suppose to look

Not all of them do, though a majority of them are only 3 fingered, its probably because it takes less time to draw 3 fingers than 5 and when you have to go frame by frame,the seconds add up.

Simpsons and Family Guy have four. Most anime, Marvel, and DC toons typically have five (or tentacles). And all I can think of for three is mew from Pokemon, and that might be two. I'm not saying that statement is invalid, but according to Stephen Colbert you might want to end it with #not intended to be a factual statement. Just sayin :)

Not ALL of them do. Especially in Superhero comics/animation and most commonly in Eastern animated work (Korean animation and Japanese anime).

But, you know, I can't help but wonder what started the 3-finger + thumb trend...