The amount of work and that goes in to computer animation of some of the characters is intense. Sulley from Monsters Inc has more than 2.3 million individual hairs, meaning a single frame took an average of 12 hours to produce.
Similarly, Rapunzel’s hair in Tangled had over 100,000 individual hairs, made even more difficult by its length. Long hair is often considered difficult and not worth the effort in CG, which is why many characters wear their hair in a bob, or braids. A single scene in Tangled could take weeks for the computer to even simulate.