All four of the Walt Disney World theme parks have height restrictions on some rides. The water parks do as well. These are for the safety of your child. If you are unsure whether or not your child is tall enough to ride have a cast member measure him at the entrance to the ride. If the height requirement is not met you can ask the same cast member about the Rider Switch option.
Disney's Animal Kingdom has a height requirement on several rides. The only theme park that has more restrictions is the Magic Kingdom. Don't worry, there are plenty of things to do at Animal Kingdom for guests of all heights. Kali River Rapids requires that guests be at least 38 inches tall. You must be at least 40 inches to ride Dinosaur. Expedition Everest - Legend of the Forbidden Mountain requires that guests be at least 44 inches tall. Guests must be 48 inches or taller to ride Primeval Whirl.