Even a classic attraction like Dumbo the Flying Elephant didn't end up as originally intended. Look closely at a vintage Dumbo from 1955- his ears are obviously not molded with the rest of his head. That's because they were intended to flap up and down while the attraction was in motion.
Unfortunately, the ears rarely worked and often caused problems with the popular attraction's daily operations. Walt Disney allowed the attraction to operate without the flapping ears. Eventually the ears on Dumbo were permanently fixed to his head. When the cars were replaced in 1990, the new models had no ear flapping mechanism.